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1.
A comparison of PMIP2 model simulations and the MARGO proxy reconstruction for tropical sea surface temperatures at last glacial maximum 总被引:2,自引:1,他引:1
Bette L. Otto-Bliesner Ralph Schneider E. C. Brady M. Kucera A. Abe-Ouchi E. Bard P. Braconnot M. Crucifix C. D. Hewitt M. Kageyama O. Marti A. Paul A. Rosell-Melé C. Waelbroeck S. L. Weber M. Weinelt Y. Yu 《Climate Dynamics》2009,32(6):799-815
Results from multiple model simulations are used to understand the tropical sea surface temperature (SST) response to the
reduced greenhouse gas concentrations and large continental ice sheets of the last glacial maximum (LGM). We present LGM simulations
from the Paleoclimate Modelling Intercomparison Project, Phase 2 (PMIP2) and compare these simulations to proxy data collated
and harmonized within the Multiproxy Approach for the Reconstruction of the Glacial Ocean Surface Project (MARGO). Five atmosphere–ocean
coupled climate models (AOGCMs) and one coupled model of intermediate complexity have PMIP2 ocean results available for LGM.
The models give a range of tropical (defined for this paper as 15°S–15°N) SST cooling of 1.0–2.4°C, comparable to the MARGO
estimate of annual cooling of 1.7 ± 1°C. The models simulate greater SST cooling in the tropical Atlantic than tropical Pacific,
but interbasin and intrabasin variations of cooling are much smaller than those found in the MARGO reconstruction. The simulated
tropical coolings are relatively insensitive to season, a feature also present in the MARGO transferred-based estimates calculated
from planktonic foraminiferal assemblages for the Indian and Pacific Oceans. These assemblages indicate seasonality in cooling
in the Atlantic basin, with greater cooling in northern summer than northern winter, not captured by the model simulations.
Biases in the simulations of the tropical upwelling and thermocline found in the preindustrial control simulations remain
for the LGM simulations and are partly responsible for the more homogeneous spatial and temporal LGM tropical cooling simulated
by the models. The PMIP2 LGM simulations give estimates for the climate sensitivity parameter of 0.67°–0.83°C per Wm−2, which translates to equilibrium climate sensitivity for doubling of atmospheric CO2 of 2.6–3.1°C. 相似文献
2.
In order to improve the reliability of climate reconstruction, especially the climatologies outside the modern observed climate
space, an improved inverse vegetation model using a recent version of BIOME4 has been designed to quantitatively reconstruct
past climates, based on pollen biome scores from the BIOME6000 project. The method has been validated with surface pollen
spectra from Eurasia and Africa, and applied to palaeoclimate reconstruction. At 6 cal ka BP (calendar years), the climate
was generally wetter than today in southern Europe and northern Africa, especially in the summer. Winter temperatures were
higher (1–5°C) than present in southern Scandinavia, northeastern Europe, and southern Africa, but cooler in southern Eurasia
and in tropical Africa, especially in Mediterranean regions. Summer temperatures were generally higher than today in most
of Eurasia and Africa, with a significant warming from ∼3 to 5°C over northwestern and southern Europe, southern Africa, and
eastern Africa. In contrast, summers were 1–3°C cooler than present in the Mediterranean lowlands and in a band from the eastern
Black Sea to Siberia. At 21 cal ka BP, a marked hydrological change can be seen in the tropical zone, where annual precipitation
was ∼200–1,000 mm/year lower than today in equatorial East Africa compared to the present. A robust inverse relationship is
shown between precipitation change and elevation in Africa. This relationship indicates that precipitation likely had an important
role in controlling equilibrium-line altitudes (ELA) changes in the tropics during the LGM period. In Eurasia, hydrological
decreases follow a longitudinal gradient from Europe to Siberia. Winter temperatures were ∼10–17°C lower than today in Eurasia
with a more significant decrease in northern regions. In Africa, winter temperature was ∼10–15°C lower than present in the
south, while it was only reduced by ∼0–3°C in the tropical zone. Comparison of palaeoclimate reconstructions using LGM and
modern CO2 concentrations reveals that the effect of CO2 on pollen-based LGM reconstructions differs by vegetation type. Reconstructions for pollen sites in steppic vegetation in
Europe show warmer winter temperatures under LGM CO2 concentrations than under modern concentrations, and reconstructions for sites in xerophytic woods/scrub in tropical high
altitude regions of Africa are wetter for LGM CO2 concentrations than for modern concentrations, because our reconstructions account for decreased plant water use efficiency. 相似文献
3.
Last Glacial Maximum climate of the former Soviet Union and Mongolia reconstructed from pollen and plant macrofossil data 总被引:2,自引:2,他引:0
P. E. Tarasov O. Peyron J. Guiot S. Brewer V. S. Volkova L. G. Bezusko N. I. Dorofeyuk E. V. Kvavadze I. M. Osipova N. K. Panova 《Climate Dynamics》1999,15(3):227-240
An improved concept of the best analogues method was used to reconstruct the Last Glacial Maximum (LGM) climate from a set
of botanical records from the former Soviet Union and Mongolia. Terrestrial pollen and macrofossil taxa were grouped into
broad classes – plant functional types (PFTs), defined by the ecological and climatic parameters used in the BIOME1 model.
PFT scores were then calibrated in terms of modern climate using 1245 surface pollen spectra from Eurasia and North America.
In contrast to individual taxa, which exhibit great variability and may not be present in the palaeoassemblages, even in suitable
climates, PFTs are more characteristic of the vegetation types. The modified method thus allows climate reconstruction at
time intervals with partial direct analogues of modern vegetation (e.g. the LGM). At 18 kBP, mean temperatures were 20–29 °C
colder than today in winter and 5–11 °C colder in summer in European Russia and Ukraine. Sites from western Georgia show negative,
but moderate temperature anomalies compared to today: 8–11 °C in January and 5–7 °C in July. LGM winters were 7–15 °C colder
and summers were 1–7 °C colder in Siberia and Mongolia. Annual precipitation sums were 50–750 mm lower than today across northern
Eurasia, suggesting a weakening of the Atlantic and Pacific influences. Reconstructed drought index shows much drier LGM conditions
in northern and mid-latitude Russia, but similar to or slightly wetter than today around the Black Sea and in Mongolia, suggesting
compensation of precipitation losses by lower-than-present evaporation.
Received: 11 May 1998 / Accepted: 25 September 1998 相似文献
4.
Quantitative reconstruction of the last interglacial vegetation and climate based on the pollen record from Lake Baikal, Russia 总被引:1,自引:0,他引:1
P. Tarasov W. Granoszewski E. Bezrukova S. Brewer M. Nita A. Abzaeva H. Oberhänsli 《Climate Dynamics》2005,25(6):625-637
Changes in mean temperature of the coldest (T
c) and warmest month (T
w), annual precipitation (P
ann) and moisture index (α) were reconstructed from a continuous pollen record from Lake Baikal, Russia. The pollen sequence
CON01-603-2 (53°57′N, 108°54′E) was recovered from a 386 m water depth in the Continent Ridge and dated to ca. 130–114.8 ky
BP. This time interval covers the complete last interglacial (LI), corresponding to MIS 5e. Results of pollen analysis and
pollen-based quantitative biome reconstruction show pronounced changes in the regional vegetation throughout the record. Shrubby
tundra covered the area at the beginning of MIS 5e (ca. 130–128 ky), consistent with the end of the Middle Pleistocene glaciation.
The late glacial climate was characterised by low winter and summer temperatures (T
c ~ −38 to −35°C and T
w~11–13°C) and low annual precipitation (P
ann~300 mm). However, the wide spread of tundra vegetation suggests rather moist environments associated with low temperatures
and evaporation (reconstructed α~1). Tundra was replaced by boreal conifer forest (taiga) by ca. 128 ky BP, suggesting a transition
to the interglacial. Taiga-dominant phase lasted until ca. 117.4 ky BP, e.g. about 10 ky. The most favourable climate conditions
occurred during the first half of the LI. P
ann reached 500 mm soon after 128 ky BP. However, temperature changed more gradually. Maximum values of T
c ~ −20°C and T
w~16–17°C are reconstructed from about 126 ky BP. Conditions became gradually colder after ca. 121 ky BP. T
c dropped to ~ −27°C and T
w to ~15°C by 119.5 ky BP. The reconstructed increase in continentality was accompanied by a decrease in P
ann to ~400–420 mm. However, the climate was still humid enough (α~0.9) to support growth of boreal evergreen conifers. A sharp
turn towards a dry climate is reconstructed after ca. 118 ky BP, causing retreat of forest and spread of cool grass-shrub
communities. Cool steppe dominated the vegetation in the area between ca. 117.5 ky and 114.8 ky BP, suggesting the end of
the interglacial and transition to the last glacial (MIS 5d). Shift to the new glaciation was characterised by cool and very
dry conditions with T
c ~ −28 to −30°C, T
w~14–15°C, P
ann~250 mm and α~0.5. 相似文献
5.
Influence of vegetation changes during the Last Glacial Maximum using the BMRC atmospheric general circulation model 总被引:3,自引:0,他引:3
The influence of different vegetation distributions on the atmospheric circulation during the Last Glacial Maximum (LGM,
21 000 years before present) is investigated. The atmospheric general circulation model of the Bureau of Meteorology Research
Center was run using a modern vegetation and in a second experiment with a vegetation reconstruction for the LGM. It is found
that a change from conifer to desert and tundra causes an additional LGM cooling of 1–2 °C in Western Europe, up to −4 °C
in North America and −6 °C in Siberia. An expansion of dryland vegetation causes an additional annual cooling of 1–2 °C for
Australia and northern Africa. On the other hand, an increase of temperature (2 °C) is found in Alaska due to changes in circulation.
In the equatorial region the LGM vegetation leads to an increased modelled temperature of 0.5–1.5 °C and decreased precipitation
(30%) over land due to a reduction of the tropical rainforest, mainly in Indonesia, where the reduction of precipitation over
land is associated with an increase of precipitation of 30% over the western Pacific.
Received: 15 December 1999 / Accepted: 10 January 2001 相似文献
6.
Alpine ecosystems in permafrost region are extremely sensitive to climate change. The headwater regions of Yangtze River and
Yellow River of the Qinghai-Tibet plateau permafrost area were selected. Spatial-temporal shifts in the extent and distribution
of tundra ecosystems were investigated for the period 1967–2000 by landscape ecological method and aerial photographs for
1967, and satellite remote sensing data (the Landsat’s TM) for 1986 and 2000. The relationships were analyzed between climate
change and the distribution area variation of tundra ecosystems and between the permafrost change and tundra ecosystems. The
responding model of tundra ecosystem to the combined effects of climate and permafrost changes was established by using statistic
regression method, and the contribution of climate changes and permafrost variation to the degradation of tundra ecosystems
was estimated. The regional climate exhibited a tendency towards significant warming and desiccation with the air temperature
increased by 0.4–0.67°C/10a and relative stable precipitation over the last 45 years. Owing to the climate continuous warming,
the intensity of surface heat source (HI) increased at the average of 0.45 W/m2 per year, the difference of surface soil temperature and air temperature (DT) increased at the range of 4.1°C–4.5°C, and
the 20-cm depth soil temperature within the active layer increased at the range of 1.1°C–1.4°C. The alpine meadow and alpine
swamp meadow were more sensitive to permafrost changes than alpine steppe. The area of alpine swamp meadow decreased by 13.6–28.9%,
while the alpine meadow area decreased by 13.5–21.3% from 1967 to 2000. The contributions of climate change to the degradation
of the alpine meadow and alpine swamp was 58–68% and 59–65% between 1967 and 2000. The synergic effects of climate change
and permafrost variation were the major drivers for the observed degradation in tundra ecosystems of the Qinghai-Tibet plateau. 相似文献
7.
We demonstrate that a hemispherically averaged upwelling-diffusion energy-balance climate model (UD/EBM) can emulate the
surface air temperature change and sea-level rise due to thermal expansion, predicted by the HadCM2 coupled atmosphere-ocean
general circulation model, for various scenarios of anthropogenic radiative forcing over 1860–2100. A climate sensitivity
of 2.6 °C is assumed, and a representation of the effect of sea-ice retreat on surface air temperature is required. In an
extended experiment, with CO2 concentration held constant at twice the control run value, the HadCM2 effective climate sensitivity is found to increase
from about 2.0 °C at the beginning of the integration to 3.85 °C after 900 years. The sea-level rise by this time is almost
1.0 m and the rate of rise fairly steady, implying that the final equilibrium value (the `commitment') is large. The base
UD/EBM can fit the 900-year simulation of surface temperature change and thermal expansion provided that the time-dependent
climate sensitivity is specified, but the vertical profile of warming in the ocean is not well reproduced. The main discrepancy
is the relatively large mid-depth warming in the HadCM2 ocean, that can be emulated by (1) diagnosing depth-dependent diffusivities
that increase through time; (2) diagnosing depth-dependent diffusivities for a pure-diffusion (zero upwelling) model; or (3)
diagnosing higher depth-dependent diffusivities that are applied to temperature perturbations only. The latter two models can be run to equilibrium, and with a climate sensitivity of 3.85 °C, they give sea-level rise
commitments of 1.7 m and 1.3 m, respectively.
Received: 27 April 1999 / Accepted: 13 September 2000 相似文献
8.
Thomas Schneider von Deimling Hermann Held Andrey Ganopolski Stefan Rahmstorf 《Climate Dynamics》2006,27(2-3):149-163
The concentration of greenhouse gases (GHGs) in the atmosphere continues to rise, hence estimating the climate system’s sensitivity to changes in GHG concentration is of vital importance. Uncertainty in climate sensitivity is a main source of uncertainty in projections of future climate change. Here we present a new approach for constraining this key uncertainty by combining ensemble simulations of the last glacial maximum (LGM) with paleo-data. For this purpose we used a climate model of intermediate complexity to perform a large set of equilibrium runs for (1) pre-industrial boundary conditions, (2) doubled CO2 concentrations, and (3) a complete set of glacial forcings (including dust and vegetation changes). Using proxy-data from the LGM at low and high latitudes we constrain the set of realistic model versions and thus climate sensitivity. We show that irrespective of uncertainties in model parameters and feedback strengths, in our model a close link exists between the simulated warming due to a doubling of CO2, and the cooling obtained for the LGM. Our results agree with recent studies that annual mean data-constraints from present day climate prove to not rule out climate sensitivities above the widely assumed sensitivity range of 1.5–4.5°C (Houghton et al. 2001). Based on our inferred close relationship between past and future temperature evolution, our study suggests that paleo-climatic data can help to reduce uncertainty in future climate projections. Our inferred uncertainty range for climate sensitivity, constrained by paleo-data, is 1.2–4.3°C and thus almost identical to the IPCC estimate. When additionally accounting for potential structural uncertainties inferred from other models the upper limit increases by about 1°C. 相似文献
9.
Past and future polar amplification of climate change: climate model intercomparisons and ice-core constraints 总被引:2,自引:2,他引:2
V. Masson-Delmotte M. Kageyama P. Braconnot S. Charbit G. Krinner C. Ritz E. Guilyardi J. Jouzel A. Abe-Ouchi M. Crucifix R. M. Gladstone C. D. Hewitt A. Kitoh A. N. LeGrande O. Marti U. Merkel T. Motoi R. Ohgaito B. Otto-Bliesner W. R. Peltier I. Ross P. J. Valdes G. Vettoretti S. L. Weber F. Wolk Y. YU 《Climate Dynamics》2006,26(5):513-529
Climate model simulations available from the PMIP1, PMIP2 and CMIP (IPCC-AR4) intercomparison projects for past and future
climate change simulations are examined in terms of polar temperature changes in comparison to global temperature changes
and with respect to pre-industrial reference simulations. For the mid-Holocene (MH, 6,000 years ago), the models are forced
by changes in the Earth’s orbital parameters. The MH PMIP1 atmosphere-only simulations conducted with sea surface temperatures
fixed to modern conditions show no MH consistent response for the poles, whereas the new PMIP2 coupled atmosphere–ocean climate
models systematically simulate a significant MH warming both for Greenland (but smaller than ice-core based estimates) and
Antarctica (consistent with the range of ice-core based range). In both PMIP1 and PMIP2, the MH annual mean changes in global
temperature are negligible, consistent with the MH orbital forcing. The simulated last glacial maximum (LGM, 21,000 years
ago) to pre-industrial change in global mean temperature ranges between 3 and 7°C in PMIP1 and PMIP2 model runs, similar to
the range of temperature change expected from a quadrupling of atmospheric CO2 concentrations in the CMIP simulations. Both LGM and future climate simulations are associated with a polar amplification
of climate change. The range of glacial polar amplification in Greenland is strongly dependent on the ice sheet elevation
changes prescribed to the climate models. All PMIP2 simulations systematically underestimate the reconstructed glacial–interglacial
Greenland temperature change, while some of the simulations do capture the reconstructed glacial–interglacial Antarctic temperature
change. Uncertainties in the prescribed central ice cap elevation cannot account for the temperature change underestimation
by climate models. The variety of climate model sensitivities enables the exploration of the relative changes in polar temperature
with respect to changes in global temperatures. Simulated changes of polar temperatures are strongly related to changes in
simulated global temperatures for both future and LGM climates, confirming that ice-core-based reconstructions provide quantitative
insights on global climate changes.
An erratum to this article can be found at 相似文献
10.
Paleo-data suggest that East African mountain treelines underwent an altitudinal shift during the Last Glacial Maximum (LGM). Understanding the ecological and physiological processes underlying treeline response to such past climate change will help to improve forecasts of treeline change under future global warming. In spite of significant improvements in paleoclimatic reconstruction, the climatic conditions explaining this migration are still debated and important factors such as atmospheric CO2 concentration, the impact of lapse rate decreasing temperature along altitudinal gradients and rainfall modifications due to elevation have often been neglected or simplified. Here, we assess the effects of these different factors and estimate the influence of the most dominant factors controlling changes in past treeline position using a multi-proxy approach based on simulations from BIOME4, a coupled biogeography and biogeochemistry model, modified to account for the effect of elevation on vegetation, compared with pollen, and isotopic data. The results indicate a shift in mountain vegetation at the LGM was controlled by low pCO2 and low temperatures promoting species morphologically and physiologically better adapted to LGM conditions than many trees composing the forest belt limit. Our estimate that the LGM climate was cooler than today’s by ?4.5 °C (range: ?4.3 to ?4.6 °C) at the upper limit of the treeline, whereas at 831 m it was cooler by ?1.4 °C (range: ?2.6 to ?0.6 °C), suggests that a possible lapse rate modification strongly constrained the upper limit of treeline, which may limit its potential extension under future global warming. 相似文献
11.
Amaelle Landais Valérie Masson-Delmotte Jean Jouzel Dominique Raynaud Sigfus Johnsen Christof Huber Markus Leuenberger Jakob Schwander Bénédicte Minster 《Climate Dynamics》2006,26(2-3):273-284
The mechanisms involved in the glacial inception are still poorly constrained due to a lack of high resolution and cross-dated
climate records at various locations. Using air isotopic measurements in the recently drilled NorthGRIP ice core, we show
that no evidence exists for stratigraphic disturbance of the climate record of the last glacial inception (∼123–100 kyears
BP) encompassing Dansgaard–Oeschger events (DO) 25, 24 and 23, even if we lack sufficient resolution to completely rule out
disturbance over DO 25. We quantify the rapid surface temperature variability over DO 23 and 24 with associated warmings of
10±2.5 and 16±2.5°C, amplitudes which mimic those observed in full glacial conditions. We use records of δ18O of O2 to propose a common timescale for the NorthGRIP and the Antarctic Vostok ice cores, with a maximum uncertainty of 2,500 years,
and to examine the interhemispheric sequence of events over this period. After a synchronous North–South temperature decrease,
the onset of rapid events is triggered in the North through DO 25. As for later events, DO 24 and 23 have a clear Antarctic
counterpart which does not seem to be the case for the very first abrupt warming (DO 25). This information, when added to
intermediate levels of CO2 and to the absence of clear ice rafting associated with DO 25, highlights the uniqueness of this first event, while DO 24
and 23 appear similar to typical full glacial DO events. 相似文献
12.
Factors controlling the magnitudes of, and short-term variations in, the potential temperatures of the snow surface and the
air at the height of 2 m θS and θ2 m over Arctic sea ice in winter are analysed. The study addresses the winters of 1986–1987 and 1987–1988, and is based on the
temperature, wind, and cloud observations made by Russian drifting ice stations. It also relies on the ERA40 re-analyses of
the European Centre for Medium-Range Weather Forecasts, which were utilised to calculate the lateral heat advection at the
sites of the ice stations. The cloud cover and wind speed were more important than the heat advection in controlling the magnitudes
of θ2 m and θS, while on a time scale of 24 h, during steady forcing conditions, the heat advection was the most important factor affecting
the changes in θS and θ2 m. During changing conditions, and considering individual factors separately, the monthly mean 24-h temperature changes were
less than ± 5 °C: the effect of the cloud cover was the largest, and that of the heat advection was the smallest. When simultaneous
changes in the three factors were analysed, the seasonal mean temperature changes were even of the order of ±15 °C, with the
strongest warming events exceeding 35 K in a single day. The difference θS − θ2 m reached its lowest seasonal mean values during conditions of clear skies (−1.3 °C), light winds (−1.3 °C) and warm-air advection
(−0.8 °C). θS and θ2 m followed each other closely, even during major synoptic-scale temperature variations. 相似文献
13.
Observed and projected climate change in Taiwan 总被引:1,自引:0,他引:1
Summary
This study examined the secular climate change characteristics in Taiwan over the past 100 years and the relationship with
the global climate change. Estimates for the likelihood of future climate changes in Taiwan were made based on the projection
from the IPCC climate models.
In the past 100 years, Taiwan experienced an island-wide warming trend (1.0–1.4 °C/100 years). Both the annual and daily temperature
ranges have also increased. The warming in Taiwan is closely connected to a large-scale circulation and SAT fluctuations,
such as the “cool ocean warm land” phenomenon. The water vapor pressure has increased significantly and could have resulted
in a larger temperature increase in summer. The probability for the occurrence of high temperatures has increased and the
result suggests that both the mean and variance in the SAT in Taiwan have changed significantly since the beginning of the
20th century. Although, as a whole, the precipitation in Taiwan has shown a tendency to increase in northern Taiwan and to
decrease in southern Taiwan in the past 100 years, it exhibits a more complicated spatial pattern. The changes occur mainly
in either the dry or rainy season and result in an enhanced seasonal cycle. The changes in temperature and precipitation are
consistent with the weakening of the East Asian monsoon.
Under consideration of both the warming effect from greenhouse gases and the cooling effect from aerosols, all projections
from climate models indicated a warmer climate near Taiwan in the future. The projected increase in the area-mean temperature
near Taiwan ranged from 0.9–2.7 °C relative to the 1961–1990 averaged temperature, when the CO2 concentration increased to 1.9 times the 1961–1990 level. These simulated temperature increases were statistically significant
and can be attributed to the radiative forcing associated with the increased concentration of greenhouse gases and aerosols.
The projected changes in precipitation were within the range of natural variability for all five models. There is no evidence
supporting the possibility of precipitation changes near Taiwan based on the simulations from five IPCC climate models.
Received February 5, 2001 Revised July 30, 2001 相似文献
14.
R. R. Reddy K. Rama Gopal L. Siva Sankara Reddy K. Narasimhulu K. Raghavendra Kumar Y. Nazeer Ahammed C. V. Krishna Reddy 《Journal of Atmospheric Chemistry》2008,59(1):47-59
In the present study, an attempt has been made to examine the governing photochemical processes of surface ozone (O3) formation in rural site. For this purpose, measurements of surface ozone and selected meteorological parameters have been
made at Anantapur (14.62°N, 77.65°E, 331 m asl), a semi-arid zone in India from January 2002 to December 2003. The annual
average diurnal variation of O3 shows maximum concentration 46 ppbv at noon and minimum 25 ppbv in the morning with 1σ standard deviation. The average seasonal
variation of ozone mixing ratios are observed to be maximum (about 60 ppbv) during summer and minimum (about 22 ppbv) in the
monsoon period. The monthly daytime and nighttime average surface ozone concentration shows a maximum (55 ± 7 ppbv; 37 ± 7.3 ppbv)
in March and minimum (28 ± 3.4 ppbv; 22 ± 2.3 ppbv) in August during the study period. The monthly average high (low) O3 48.9 ± 7.7 ppbv (26.2 ± 3.5 ppbv) observed at noon in March (August) is due to the possible increase in precursor gas concentration
by anthropogenic activity and the influence of meteorological parameters. The rate of increase of surface ozone is high (1.52 ppbv/h)
in March and lower (0.40 ppbv/h) in July. The average rate of increase of O3 from midnight to midday is 1 ppbv/h. Surface temperature is highest (43–44°C) during March and April months leading to higher
photochemical production. On the other hand, relative humidity, which is higher during the rainy season, shows negative correlation
with temperature and ozone mixing ratio. It can be seen that among the two parameters are measured, correlation of surface
ozone with wind speed is better (R
2=0.84) in compare with relative humidity (R
2=0.66). 相似文献
15.
Seong-Joong Kim Thomas J. Crowley David J. Erickson Bala Govindasamy Phillip B. Duffy Bang Yong Lee 《Climate Dynamics》2008,31(1):1-16
The climate of the last glacial maximum (LGM) is simulated with a high-resolution atmospheric general circulation model, the
NCAR CCM3 at spectral truncation of T170, corresponding to a grid cell size of roughly 75 km. The purpose of the study is
to assess whether there are significant benefits from the higher resolution simulation compared to the lower resolution simulation
associated with the role of topography. The LGM simulations were forced with modified CLIMAP sea ice distribution and sea
surface temperatures (SST) reduced by 1°C, ice sheet topography, reduced CO2, and 21,000 BP orbital parameters. The high-resolution model captures modern climate reasonably well, in particular the distribution
of heavy precipitation in the tropical Pacific. For the ice age case, surface temperature simulated by the high-resolution
model agrees better with those of proxy estimates than does the low-resolution model. Despite the fact that tropical SSTs
were only 2.1°C less than the control run, there are many lowland tropical land areas 4–6°C colder than present. Comparison
of T170 model results with the best constrained proxy temperature estimates (noble gas concentrations in groundwater) now
yield no significant differences between model and observations. There are also significant upland temperature changes in
the best resolved tropical mountain belt (the Andes). We provisionally attribute this result in part as resulting from decreased
lateral mixing between ocean and land in a model with more model grid cells. A longstanding model-data discrepancy therefore
appears to be resolved without invoking any unusual model physics. The response of the Asian summer monsoon can also be more
clearly linked to local geography in the high-resolution model than in the low-resolution model; this distinction should enable
more confident validation of climate proxy data with the high-resolution model. Elsewhere, an inferred salinity increase in
the subtropical North Atlantic may have significant implications for ocean circulation changes during the LGM. A large part
of the Amazon and Congo Basins are simulated to be substantially drier in the ice age—consistent with many (but not all) paleo
data. These results suggest that there are considerable benefits derived from high-resolution model regarding regional climate
responses, and that observationalists can now compare their results with models that resolve geography at a resolution comparable
to that which the proxy data represent. 相似文献
16.
The spatial and temporal variability of land carbon flux over the past one hundred years was investigated based on an empirical
model directly calculating soil respiration rate. Our model shows that during 1901–1995, about 44-89 PgC (equals to 0.5, 0.9
PgC/yr respectively) were absorbed by terrestrial biosphere. The simulated net ecosystem productivity (NEP) after the 1930s
was close to the estimated value of “ missing C sink” from deconvolution analysis. Most of the total carbon sink happened
during 1951–1985 with the estimated value of 33–50 PgC. Three major sinks were located in the tropics (10°S–10°N), Northern
mid-latitudes (30°–60°N) and Southern subtropics (10°–40°S). During 1940s-mid-1970s, carbon sinks by terrestrial ecosystem
increased with time, and decreased after the mid-1970s. These may be due to the changing of climate condition, as during the
1940s–1970s, temperature decreased and precipitation increased, while after the mid-1970s, an opposite climate situation occurred
with evident increasing in temperature and decreasing in precipitation. Usually, warmer and dryer climate condition is not
favor for carbon absorption by biosphere and even induces net carbon release from soil, while cooler and wetter condition
may induce more carbon sink. Our model results show that the net carbon flux is particularly dependent on moisture / precipitation
effect despite of temperature effect. The changing of climate in the past century may be a possible factor inducing increases
in carbon sink in addition to CO2 and N fertilizer.
This research was funded by CAS One Hundred Talents project and Knowledge Innovation Project of CAS(KZCX2-201). 相似文献
17.
Palaeoclimates across Europe for 6000 y BP were estimated from pollen data using the modern pollen analogue technique constrained
with lake-level data. The constraint consists of restricting the set of modern pollen samples considered as analogues of the
fossil samples to those locations where the implied change in annual precipitation minus evapotranspiration (P–E) is consistent with the regional change in moisture balance as indicated by lakes. An artificial neural network was used
for the spatial interpolation of lake-level changes to the pollen sites, and for mapping palaeoclimate anomalies. The climate
variables reconstructed were mean temperature of the coldest month (T
c
), growing degree days above 5 °C (GDD), moisture availability expressed as the ratio of actual to equilibrium evapotranspiration (α), and P–E. The constraint improved the spatial coherency of the reconstructed palaeoclimate anomalies, especially for P–E. The reconstructions indicate clear spatial and seasonal patterns of Holocene climate change, which can provide a quantitative
benchmark for the evaluation of palaeoclimate model simulations. Winter temperatures (T
c
) were 1–3 K greater than present in the far N and NE of Europe, but 2–4 K less than present in the Mediterranean region.
Summer warmth (GDD) was greater than present in NW Europe (by 400–800 K day at the highest elevations) and in the Alps, but >400 K day less
than present at lower elevations in S Europe. P–E was 50–250 mm less than present in NW Europe and the Alps, but α was 10–15% greater than present in S Europe and P–E was 50–200 mm greater than present in S and E Europe.
Received: 3 January 1996 / Accepted: 15 July 1996 相似文献
18.
Scenarios indicate that the air temperature will increase in high latitude regions in coming decades, causing the snow covered
period to shorten, the growing season to lengthen and soil temperatures to change during the winter, spring and early summer.
To evaluate how a warmer climate is likely to alter the snow cover and soil temperature in Scots pine stands of varying ages
in northern Sweden, climate scenarios from the Swedish regional climate modelling programme SWECLIM were used to drive a Soil-Vegetation-Atmosphere
Transfer (SVAT)-model (COUP). Using the two CO2 emission scenarios A and B in the Hadley centres global climate model, HadleyA and HadleyB, SWECLIM predicts that the annual
mean air temperature and precipitation will increase at most 4.8°C and 315 mm, respectively, within a century in the study
region. The results of this analysis indicate that a warmer climate will shorten the period of persistent snow pack by 73–93 days,
increase the average soil temperature by 0.9–1.5°C at 10 cm depth, advance soil warming by 15–19 days in spring and cause
more soil freeze–thaw cycles by 31–38%. The results also predict that the large current variations in snow cover due to variations
in tree interception and topography will be enhanced in the coming century, resulting in increased spatial variability in
soil temperatures. 相似文献
19.
The equilibrium climate response to anthropogenic forcing has long been one of the dominant, and therefore most intensively studied, uncertainties in predicting future climate change. As a result, many probabilistic estimates of the climate sensitivity (S) have been presented. In recent years, most of them have assigned significant probability to extremely high sensitivity, such as P(S?>?6C)?>?5%. In this paper, we investigate some of the assumptions underlying these estimates. We show that the popular choice of a uniform prior has unacceptable properties and cannot be reasonably considered to generate meaningful and usable results. When instead reasonable assumptions are made, much greater confidence in a moderate value for S is easily justified, with an upper 95% probability limit for S easily shown to lie close to 4°C, and certainly well below 6°C. These results also impact strongly on projected economic losses due to climate change. 相似文献
20.
Michelle T. H. van Vliet Stephen Blenkinsop Aidan Burton Colin Harpham Hans Peter Broers Hayley J. Fowler 《Climatic change》2012,111(2):249-277
Regional or local scale hydrological impact studies require high resolution climate change scenarios which should incorporate
some assessment of uncertainties in future climate projections. This paper describes a method used to produce a multi-model
ensemble of multivariate weather simulations including spatial–temporal rainfall scenarios and single-site temperature and
potential evapotranspiration scenarios for hydrological impact assessment in the Dommel catchment (1,350 km2) in The Netherlands and Belgium. A multi-site stochastic rainfall model combined with a rainfall conditioned weather generator
have been used for the first time with the change factor approach to downscale projections of change derived from eight Regional
Climate Model (RCM) experiments for the SRES A2 emission scenario for the period 2071–2100. For winter, all downscaled scenarios
show an increase in mean daily precipitation (catchment average change of +9% to +40%) and typically an increase in the proportion
of wet days, while for summer a decrease in mean daily precipitation (−16% to −57%) and proportion of wet days is projected.
The range of projected mean temperature is 7.7°C to 9.1°C for winter and 19.9°C to 23.3°C for summer, relative to means for
the control period (1961–1990) of 3.8°C and 16.8°C, respectively. Mean annual potential evapotranspiration is projected to
increase by between +17% and +36%. The magnitude and seasonal distribution of changes in the downscaled climate change projections
are strongly influenced by the General Circulation Model (GCM) providing boundary conditions for the RCM experiments. Therefore,
a multi-model ensemble of climate change scenarios based on different RCMs and GCMs provides more robust estimates of precipitation,
temperature and evapotranspiration for hydrological impact assessments, at both regional and local scale. 相似文献