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1.
Records of UV data started in Madrid at the beginning of the 90's decade. After some quality control on the data a seven year period from 1996 to 2002 was selected to perform an analysis of daily and seasonal variability of solar ultraviolet B (UVB) values at the centre of the Iberian Peninsula. Instruments used are a Brewer MKIV spectrophotometer and a YES UVB-1 broadband pyranometer. Both instruments provided integrated daily values according with the Diffey spectrum although they have different measurement procedures. Data statistics from each instrument for the same period and statistical relationships between daily values from both instruments are shown. As broadband YES provided a record with fewer time gaps, analysis of UVI extreme values is performed using that instrument. The relationship between UVB values with ozone, cloudiness and visible radiation has been described in several papers for different places in the world. In this paper, those relationships are shown for Madrid. A discussion about specific problems found when trying to isolate every effective factor is also included. Some of those relationships could be helpful to retrieve UVB values from other ancillary data as visible radiation and cloudiness. Finally, a detailed study for 10 days in June 1997 when the maximum record of daily values from the present time series was obtained, highlight the close correlation between total ozone content and the daily variability of UVB for similar amounts of incoming radiation. 相似文献
2.
J. C. González Hidalgo M. De Luís J. Raventós J. R. Sánchez 《Theoretical and Applied Climatology》2003,75(1-2):117-130
Summary ?We have analyzed daily rainfall trends throughout the second half of the 20th century in the western Mediterranean basin (Valencia Region, E of Spain). The area is characterized by high torrentiality,
and during the second half of the 20th century some of the highest daily rainfall values in the Mediterranean basin have been recorded. In this area, mean annual
rainfall varies between 500 and 300 mm and is overwhelmingly dependent on just a few days of rain. Daily maximum rainfall
varies on average from 120 mm day−1 to 50 mm day−1, and represents a mean of 17% (coastland) to 9% (inland) of annual rainfall. The 10 days in each year with the heaviest rainfall
(called “higher events”) provide over 50% of the annual rainfall and can reach more than 400 mm on average. We compared the
annual rainfall trend and the trend of higher and minor events defined by percentiles, both in volume and variability. We,
therefore, tested whether annual rainfall changes depend on the trend of the higher (rainfall) events.
To overlap spatial distribution of trends (i.e.: positive, no significant and negative trends) we have used cross-tab analysis.
The results confirm the hypothesis that annual rainfall changes depend on changes found in just a few rainy events. Furthermore,
in spite of their negative trend, higher events have increased their contribution to annual rainfall.
As a consequence, although torrential events may have diminished in magnitude, future scenarios seem to be controlled by a
limited number of rainy events which will become more and more variable year on year. The high spatial density of data used
in this work, (97 observatories per 24.000 km2, overall mean 1 observatory per 200 km2), suggests to us that extreme caution should be applied when analyzing regional and sub-regional changes in rainfall using
GCM output, especially in areas of high torrentiality.
Received August 1, 2002; revised November 11, 2002; accepted December 1, 2002
Published online May 19, 2003 相似文献
3.
Summary ?The analysis of ground-based measurements of solar erythemal ultraviolet (UV) irradiance with a Solar Light 501 biometer,
and total (300–3000 nm) irradiance with an Eppley B&W pyranometer at the Argentine Antarctic Base “Almirante Brown”, Paradise
Bay (64.9° S, 62.9° W, 10 m a.s.l.) is presented. Measurement period extends from February 16 to March 28 2000. A relatively
high mean albedo and a very clean atmosphere characterise the place. Sky conditions were of generally high cloud cover percentage.
Clear-sky irradiance for each day was estimated with model calculations, and the effect of the cloudiness was studied through
the ratio of measured to clear-sky value (r). Two particular cases were analysed: overcast sky without precipitation and overcast sky with rain or slight snowfall, the
last one presenting frequently dense fog. Total irradiance was more attenuated than UV by the homogeneous cloudiness, obtaining
mean r values of 0.54 for erythemal irradiance and 0.30 for total irradiance in the first case (without precipitation) and 0.27
and 0.17 respectively in the second case (with precipitation). Mean r values for the complete period were 0.58 for erythemal irradiance and 0.43 for total irradiance. Erythemal and total daily
insolations reduce quickly at this epoch due to the increase of the noon solar zenith angle and the decrease of daylight time.
Additionally, they were strongly modulated by cloudiness. Measured maxima were 2.71 kJ/m2 and 18.42 MJ/m2 respectively. Measurements were compared with satellite data. TOMS-inferred erythemal daily insolation shows the typical
underestimation with respect to ground measurements at regions of high mean albedo. Measured mean total daily insolation agrees
with climatological satellite data for the months of the campaign.
Received August 9, 2002; revised January 4, 2003; accepted January 28, 2003
Published online May 20, 2003 相似文献
4.
D. R. Kothawale A. A. Munot H. P. Borgaonkar 《Theoretical and Applied Climatology》2008,92(1-2):31-45
Summary The present study examines the long term trend in sea surface temperatures (SSTs) of the Arabian Sea, Bay of Bengal and Equatorial
South India Ocean in the context of global warming for the period 1901–2002 and for a subset period 1971–2002. An attempt
has also been made to identify the relationship between SST variations over three different ocean areas, and All-India and
homogeneous region summer monsoon rainfall variability, including the role of El-Ni?o/Southern Oscillation (ENSO). Annual
sea surface temperatures of the Arabian Sea, Bay of Bengal and Equatorial South India Ocean show a significant warming trend
of 0.7 °C, 0.6 °C and 0.5 °C per hundred years, respectively, and a relatively accelerated warming of 0.16 °C, 0.14 °C and
0.14 °C per decade during the 1971–2002 period.
There is a positive and statistically significant relationship between SSTs over the Arabian Sea from the preceding November
to the current February, and Indian monsoon rainfall during the period 1901–2002. The correlation coefficient increases from
October and peaks in December, decreasing from February to September. This significant relationship is also found in the recent
period 1971–2002, whereas, during 1901–70, the relationship is not significant. On the seasonal scale, Arabian Sea winter
SSTs are positively and significantly correlated with Indian monsoon rainfall, while spring SSTs have no significant positive
relationship. Nino3 spring SSTs have a negative significant relationship with Indian monsoon rainfall and it is postulated
that there is a combined effect of Nino3 and Arabian Sea SSTs on Indian monsoon. If the Nino3 SST effect is removed, the spring
SSTs over the Arabian Sea also have a significant relationship with monsoon rainfall. Similarly, the Bay of Bengal and Equatorial
South Indian Ocean spring SSTs are significantly and positively correlated with Indian monsoon rainfall after removing the
Nino3 effect, and correlation values are more pronounced than for the Arabian Sea.
Authors’ address: Dr. D. R. Kothawale, A. A. Munot, H. P. Borgaonkar, Climatology and Hydrometeorology divisions, Indian Institute
of Tropical Meteorology, Pune 411008, India. 相似文献
5.
Absorption and fluorescence properties of rainwater during the cold season at a town in Western Portugal 总被引:1,自引:0,他引:1
Patrícia S. M. Santos Regina M. B. O. Duarte Armando C. Duarte 《Journal of Atmospheric Chemistry》2009,62(1):45-57
This study aims at evaluating the variability of the optical properties of chromophoric dissolved organic matter (CDOM) of
rainwater during the cold season, specifically between Autumn and Winter periods. The spectroscopic characteristics of rainwater
samples collected at a town (Aveiro) in western Portugal were assessed by UV-Vis absorbance and three-dimensional excitation-emission
matrix (EEM) fluorescence spectroscopies. Rainwater samples showed similar characteristics to those of natural humic substances
when analysed by UV-Vis absorbance spectroscopy, but a significant difference was observed in the volume weight average (VWA)
of absorbances between Autumn and Winter. In general, the EEM fluorescence spectra of the Autumn and Winter samples disclosed
the presence of six fluorophores with different VWA specific fluorescence intensities: three humic-like (λ
excitation/λ
emission ≈ 230/415 nm; 290/415 nm; and 340/415 nm) and three protein-like (λ
excitation/λ
emission ≈ 230/350 nm; 280/340 nm; and 225/300 nm), but one of the humic-like peaks (≈340/415 nm) does not always appear in the EEM
fluorescence spectra of the Winter samples. During the cold season, chromophoric compounds are important constituents of rainwater
dissolved organic matter and the presence of these highly absorbing and fluorescing compounds may exert a determining effect
in atmospheric absorption of solar radiation. 相似文献
6.
Summary ?This paper presents an objective analysis of the structure of daily rainfall variability over the South American/South Atlantic
region (15°–60° W and 0°–40° S) during individual austral summer months of November to March. From EOF analysis of satellite
derived daily rainfall we find that the leading mode of variability is represented by a highly coherent meridional dipole
structure, organised into 2 extensive bands, oriented northwest to southeast across the continent and Atlantic Ocean. We argue
that this dipole structure represents variability in the meridional position of the South Atlantic Convergence Zone (SACZ).
During early and later summer, in the positive (negative) phase of the dipole, enhanced (suppressed) rainfall over eastern
tropical Brazil links with that over the subtropical and extra-tropical Atlantic and is associated with suppressed (enhanced)
rainfall over the sub-tropical plains and adjacent Atlantic Ocean. This structure is indicative of interaction between the
tropical, subtropical and temperate zones. Composite fields from NCEP reanalysis products (associated with the major positive
and negative events) show that in early and late summer the position of the SACZ is associated with variability in: (a) the
midlatitude wave structure, (b) the position of the continental low, and (c) the zonal position of the South Atlantic Subtropical
High. Harmonic analysis of the 200 hPa geopotential anomaly structure in the midlatitudes indicates that reversals in the
rainfall dipole structure are associated primarily with variability in zonal wave 4. There is evidence of a wave train extending
throughout the midlatitudes from the western Pacific into the SACZ region. During positive (negative) events the largest anomalous
moisture advection occurs within westerlies (easterlies) primarily from Amazonia (the South Atlantic). In both phases a convergent
poleward flow results along the leading edge of the low-level trough extending from the tropics into temperate latitudes.
High summer events differ from those in early and late summer in that the rainfall dipole is primarily associated with variability
in the phase of zonal wave 3, and that tropical-temperate link is not clearly evident in positive events.
Received May 31, 2001; revised October 17, 2001; accepted June 13, 2002 相似文献
7.
Summary ?The dependence of aerosol optical depth on wavelength as well as the fit of the ?ngstr?m approximation have been investigated
under different air masses at a sub-Arctic location (Abisko, Sweden; 68° 21′ N, 18° 49′ E) and a tropical environment (Ife,
Nigeria; 7° 30′ N, 4° 31′ E). The study is based on spectral data acquired with a high resolution spectral radiometer (spectral
range: 300–1100 nm) in absorption-free regions.
The wavelength dependence of the aerosols under different air mass conditions at the sub-arctic location offer significant
contrasts to aerosols of Saharan origin at Ife. A general characteristic of the aerosol optical depth spectra after the Pinatubo
volcanic eruption was a much weaker wavelength dependence relative to pre-Pinatubo conditions.
Categorising the features of the optical depth spectra according to their wavelength dependence, three main groups were observed
at Abisko, while two main classes have been discussed for the harmattan season in the tropical climate of Ife and environs.
For the first two groups in Abisko (and the first group at Ife), aerosol optical depth generally decreased with wavelength
while the third group (second group at Ife) exhibited strong curvatures.
The correlation coefficient obtained from the regression equation of the ?ngstr?m equation, has been shown to be a good index
of the general fit of the ?ngstr?m approximation for the three groups at Abisko, but much weaker for the harmattan conditions
at the tropical location. Although the probability of systematic deviations from the ?ngstr?m law is highest under intense
harmattan conditions with considerably high β and low α, it has been observed that the ?ngstr?m fit was good in many highly
turbid conditions at the tropical site. Hence, apart from the level of turbidity, the applicability of the ?ngstr?m approximation
is strongly dependent on aerosol characteristics and source region.
Formerly Adeyefa.
Received May 18, 2001; revised June 20, 2002; accepted August 5, 2002 相似文献
8.
Interannual variability and predictability in an ensemble of AMIP climate simulations conducted with the CCC GCM2 总被引:2,自引:0,他引:2
F. W. Zwiers 《Climate Dynamics》1996,12(12):825-847
This study considers an ensemble of six 10-year climate simulations conducted with the Canadian Climate Centre 2nd generation
General Circulation Model (CCC GCM2). Each simulation was forced according to the Atmospheric Model Intercomparison Project
(AMIP) experimental protocol using monthly mean sea surface temperatures and sea-ice extents based on observations for January,
1979 to December 1988. One simulation, conducted on a CRAY computer, was initiated from analysed 1 January 1979 conditions
while the remaining 5 simulations, conducted on a NEC computer, were initiated from previously simulated model states obtained
from a long control integration. The interannual variability and potential predictability of simulated and observed 500 hPa
geopotential, 850 hPa temperature and 300 hPa stream function are examined and inter-compared using statistical analysis of
variance techniques to partition variance into a number of components. The boundary conditions specified by AMIP are found
to induce statistically significant amounts of predictable variance on the interannual time scale in the tropics and, to a
lesser extent, at extratropical latitudes. In addition, local interactions between the atmosphere and the land surface apparently
induce significant amounts of potentially predictable interannual variance in the tropical lower atmosphere and also at some
locations in the temperate lower atmosphere. No evidence was found that the atmosphere's internal dynamics on their own generate
potentially predictable variations on the interannual time scale. The sensitivity of the statistical methods used is demonstrated
by the fact that we are able to detect differences between the climates simulated on the two computers used. The causes of
these physically insignificant changes are traced. The statistical procedures are checked by confirming that the choice of
initial conditions does not lead to significant inter-simulation variation. The simulations are also interpreted as an ensemble
of climate forecasts that rely only on the specified boundary conditions for their predictive skill. The forecasts are verified
against observations and against themselves. In agreement with other studies it was found that the forecasts have very high
skill in the tropics and moderate skill in the extratropics.
Received: 18 December 1995 / Accepted: 4 April 1996 相似文献
9.
B. Geerts 《Theoretical and Applied Climatology》2003,74(3-4):145-165
Summary ?This is a sequel to a study of the empirical estimation of the annual mean temperature and its range, at any location on
land, based on the historical surface climate record. Here the spatial patterns of the daily temperature range (DTR) and its
seasonal variation are examined. The DTR is highest in the subtropical deserts and is less at high latitudes, as well as within
30–150 km from an ocean. It is generally higher in winter (summer) at low (high) latitudes. The coastal DTR reduction is explained
by sea breezes, onshore advection, and low-level cloud cover. Even large bodies of water, such as Lake Michigan, affect the
near-shore DTR. Elevation does not directly affect the DTR, but valleys tend to have a DTR that is 2–6 K larger than adjacent
hills or ridges.
The main factor affecting the DTR is the afternoon relative humidity, which is dynamically linked to low-level cloud cover.
An empirical relationship between DTR and afternoon relative humidity has an uncertainty of about 1.4 K for monthly-mean values.
Received March 6, 2002; revised September 20, 2002; accepted November 3, 2002 相似文献
10.
C. V. Singh 《Theoretical and Applied Climatology》2006,84(4):207-211
Summary In this study, Principal Component Analysis (PCA) has been used to identify the major modes of the outgoing long-wave radiation
data for the period (1979–2002) during the Indian monsoon period (June–September), using seasonal mean values over the Indian
region covering 143 grid points (5° N–35° N and 70° E–95° E at 2.5° Longitude–Latitude intervals. The five principal components
explain up to 98.0% of the total variance. The first principal component explains 60% of the total variance with a pronounced
variation in the outgoing long-wave radiation over the region 10° N to 25° N. It appears that the major reason for the monsoon
variability is the intensity and associated fluctuations in the two major semi-permanent seasonal systems. This is largely
indicative of strong seasonal shift of the major area of cloudiness associated with convergence zone. The second principal
component explaining 20% of the total variance exhibits higher positive component loadings along 25° N and east of 80° E.
The possible reason for this could be the synoptic systems such as monsoon depression/lows over the north bay and trough/vortices
off the west-coast in the Arabian sea. 相似文献
11.
Forecast skill as a function of the ensemble size is examined in a 24-member ensemble of northern winter (DJF) hindcasts
produced with the second generation general circulation model of the Canadian Centre for Climate Modelling and Analysis. These
integrations are initialized from the NCEP reanalyses at 6 h intervals prior to the forecast season. The sea surface temperatures
that are applied as lower boundary conditions are predicted by persisting the monthly mean anomaly observed prior to the forecast
period. The potential predictability that is attributed to lower boundary forced variability is estimated. In lagged-average
forecasting, the forecast skill in the first two weeks, which originates predominately from the initial conditions, is greatest
for relatively small ensemble sizes. The forecast skill increases monotonically with the ensemble size in the rest of the
season. The skill of DJF 500 hPa geopotential height hindcasts in the Northern Hemisphere and in the Pacific/North America
sector improves substantially when the ensemble size increases from 6 to 24. A statistical skill improvement technique based
on the singular value decomposition method is also more successful for larger ensembles.
Received: 22 February 2000 / Accepted: 6 December 2000 相似文献
12.
Summary ?One hundred and thirty six years (1856–1991) of monthly sea-surface temperature (SST) data in the Tropical Atlantic Ocean
are used to investigate the propagating signals of the SST at a decadal (DD) time scale. The first and the third evolving
modes show a relationship between the equatorial and the inter-hemispheric patterns, one evolving into the other mode and
vice-versa. These modes describe two different evolutions of the SST at DD time-scale. The first EEOF features a 12-year period
oscillatory regime with a strong 2-year duration inter-hemispheric pattern evolving into a weak 1-year duration equatorial
pattern and vice-versa. This mode exhibits also a northward displacement of the anomalies in the band 15° S–15° N. The third
EEOF also shows an oscillatory regime, but with a period of 10 years and with a relatively strong 2-year duration equatorial
pattern evolving into a weak 1-year duration inter-hemispheric pattern and vice-versa. For this mode, the SST anomalies show
a southward displacement in the band 15° S–15° N. These results have not yet been documented in previous works and explain
some of the previous findings on the DD variability in the Tropical Atlantic.
Received December 31, 2001; revised April 9, 2002; accepted September 4, 2002
Published online: March 20, 2003 相似文献
13.
Summary By analyzing 12-year (1979–1990) 200 hPa wind data from National Centers for Environmental Prediction-National Center for
Atmospheric Research reanalysis, we demonstrate that the intraseasonal time scale (30–60 days) variability of the Tropical
Easterly Jet (TEJ) reported in individual case studies occurs during most years. In the entrance region (east of ∼70° E),
axis of the TEJ at 200 hPa is found along the near equatorial latitudes during monsoon onset/monsoon revivals and propagates
northward as the monsoon advances over India. This axis is found along ∼5° N and ∼15° N during active monsoon and break monsoon
conditions respectively. Examination of the European Centre for Medium Range Weather Forecasts reanalysis wind data also confirms
the northward propagation of the TEJ on intraseasonal time scales.
During the intraseasonal northward propagations, axis of the TEJ is found about 10°–15° latitudes south of the well-known
intraseasonally northward propagating monsoon convective belts. Because of this 10°–15° displacement, axis of the TEJ arrives
over a location about two weeks after the arrival of the monsoon convection. Systematic shifting of the locations by convection,
low level monsoon flow and TEJ in a collective way during different phases of the monsoon suggests that they all may be related. 相似文献
14.
Summary ?Above orographically structured terrain considerable differences of the regional wind field may be identified during large-scale
extreme wind events. So far, these regional differences could not be resolved by climate models. To determine the relationships
between large-scale atmospheric conditions, the influence of orography, and the regional wind field, data measured in the
upper Rhine valley within the framework of the REKLIP Regional Climate Project were analyzed and calculations were made using
the KAMM mesoscale model. In the area of the upper Rhine valley, ratios of the wind velocity in the Rhine valley at 10 m above
ground level, νval, and the large-scale flow velocity, νlar, are between νval/νlar ≈ 0.1 and νval/νlar ≈ 1. The νval/νlar ratio exhibits a strong dependence on thermal stratification, δ, and decreases from νval/νlar ≈ 1 at δ = 0 K m−1 to νval/νlar ≈ 0.2 at δ = 0.0075 K m−1. In areas, where the lateral mountainous border of the Rhine valley is interrupted, the νval/νlar ratio increases again with increasing stability or decreasing Froude number. This is obviously due to flow around the Black
Forest under stable stratification. It is demonstrated by model calculations that a complex wind field develops in the Rhine
valley at small Froude numbers (Fr < 1) irrespective of the direction of large-scale flow. The νval/νlar ratio is characterized by small values in the direct lee side (νval/νlar ≈ 0.2) and high values on the windward side of the lateral mountainous border of the Rhine valley (νval/νlar ≈ 0.8).
Received October 22, 2001; revised June 18, 2002; accepted June 23, 2002 相似文献
15.
Summary Net ecosystem CO2 exchange was measured over a mountain birch forest in northern Finland throughout the growing season. The maximal net CO2 uptake rate of about − 0.5 mg(CO2) m−2 s−1 was observed at the end of July. The highest nocturnal respiration rates in early August were 0.2 mg(CO2) m−2 s−1. The daily CO2 balances during the time of maximal photosynthesis were about −15 g(CO2) m−2 d−1. The mountain birch forest acted as a net sink of CO2 from 30 June to 28 August. During that period the net CO2 balance was −448 g(CO2)m−2. The interannual representativeness of the observed balances was studied using a simplified daily balance model, with daily
mean global radiation and air temperature as the input parameters. The year-to-year variation in the phenological development
was parameterised as a function of the cumulative effective temperature sum. The daily balance model was used for estimating
the variability in the seasonal CO2 balances due to the timing of spring and meteorological factors. The sink term of CO2 in 1996 was lower than the 15-year mean, mainly due to the relatively late emergence of the leaves.
Received October 11, 1999 Revised April 25, 2000 相似文献
16.
Jonghan Ko Lajpat R. Ahuja S. A. Saseendran Timothy R. Green Liwang Ma David C. Nielsen Charles L. Walthall 《Climatic change》2012,111(2):445-472
Agricultural systems models are essential tools to assess potential climate change (CC) impacts on crop production and help
guide policy decisions. In this study, impacts of projected CC on dryland crop rotations of wheat-fallow (WF), wheat-corn-fallow
(WCF), and wheat-corn-millet (WCM) in the U.S. Central Great Plains (Akron, Colorado) were simulated using the CERES V4.0
crop modules in RZWQM2. The CC scenarios for CO2, temperature and precipitation were based on a synthesis of Intergovernmental Panel on Climate Change (IPCC 2007) projections for Colorado. The CC for years 2025, 2050, 2075, and 2100 (CC projection years) were super-imposed on measured
baseline climate data for 15–17 years collected during the long-term WF and WCF (1992–2008), and WCM (1994–2008) experiments
at the location to provide inter-annual variability. For all the CC projection years, a decline in simulated wheat yield and
an increase in actual transpiration were observed, but compared to the baseline these changes were not significant (p > 0.05) in all cases but one. However, corn and proso millet yields in all rotations and projection years declined significantly
(p < 0.05), which resulted in decreased transpiration. Overall, the projected negative effects of rising temperatures on crop
production dominated over any positive impacts of atmospheric CO2 increases in these dryland cropping systems. Simulated adaptation via changes in planting dates did not mitigate the yield
losses of the crops significantly. However, the no-tillage maintained higher wheat yields than the conventional tillage in
the WF rotation to year 2075. Possible effects of historical CO2 increases during the past century (from 300 to 380 ppm) on crop yields were also simulated using 96 years of measured climate
data (1912–2008) at the location. On average the CO2 increase enhanced wheat yields by about 30%, and millet yields by about 17%, with no significant changes in corn yields. 相似文献
17.
Arun Chakraborty H. C. Upadhyaya O. P. Sharma Divya Jaisawal S. K. Deb 《Meteorology and Atmospheric Physics》2003,83(3-4):197-220
Summary ?A three-dimensional Ocean General Circulation Model has been developed in stretched coordinate from scratch. The same model
has been used to perform some numerical experiments to simulate the basic circulation pattern and the model variability to
atmospheric forcing. For numerical simulations 72 × 25 grid points in the horizontal directions and nine (10, 30, 75, 250,
500, 1000, 1500, 2000 and 3000 m) vertical levels are considered. The lateral boundaries are set at 60° N and 60° S. The basic
focus of the paper is on the demonstration of the performance of the model and its assessment by employing appropriate forcing
from the outputs of an atmospheric general circulation model. Hence, the model was forced with the forcing (wind and thermodynamic)
derived from the ECMWF runs from the AMIP archives. The preliminary results show the realistic simulation of basic pattern
of different fields. The model simulations show that the model is able to reproduce some of the general features of the ocean,
such as surface currents, surface temperature and salinity, mass transport and meridional heat transport. It is also to be
noted that the model is capable to capture the El-Ni?o and La-Ni?a type events.
Received April 3, 2002; revised June 6, 2002; accepted July 24, 2002
Published online: February 20, 2003 相似文献
18.
Stratospheric zonal wind and temperature in relation to summer monsoon rainfall over India 总被引:1,自引:0,他引:1
Summary The interannual variability of the Indian summer monsoon (June–September) rainfall is examined in relation to the stratospheric
zonal wind and temperature fluctuations at three stations, widely spaced apart. The data analyzed are for Balboa, Ascension
and Singapore, equatorial stations using recent period (1964–1994) data, at each of the 10, 30 and 50 hPa levels. The 10 hPa
zonal wind for Balboa and Ascension during January and the 30 hPa zonal wind for Balboa during April are found to be positively
correlated with the subsequent Indian summer monsoon rainfall, whereas the temperature at 10 hPa for Ascension during May
is negatively correlated with Indian summer monsoon rainfall. The relationship with stratospheric temperatures appears to
be the best, and is found to be stable over the period of analysis.
Stratospheric temperature is also significantly correlated with the summer monsoon rainfall over a large and coherent region,
in the north-west of India. Thus, the 10 hPa temperature for Ascension in May appears to be useful for forecasting summer
monsoon rainfall for not only the whole of India, but also for a smaller region lying to the north-west of India.
Received July 30, 1999 Revised March 17, 2000 相似文献
19.
A transient climate change simulation with greenhouse gas and aerosol forcing: projected climate to the twenty-first century 总被引:3,自引:0,他引:3
The potential climatic consequences of increasing atmospheric greenhouse gas (GHG) concentration and sulfate aerosol loading
are investigated for the years 1900 to 2100 based on five simulations with the CCCma coupled climate model. The five simulations
comprise a control experiment without change in GHG or aerosol amount, three independent simulations with increasing GHG and
aerosol forcing, and a simulation with increasing GHG forcing only. Climate warming accelerates from the present with global
mean temperatures simulated to increase by 1.7 °C to the year 2050 and by a further 2.7 °C by the year 2100. The warming is
non-uniform as to hemisphere, season, and underlying surface. Changes in interannual variability of temperature show considerable
structure and seasonal dependence. The effect of the comparatively localized negative radiative forcing associated with the
aerosol is to retard and reduce the warming by about 0.9 °C at 2050 and 1.2 °C at 2100. Its primary effect on temperature
is to counteract the global pattern of GHG-induced warming and only secondarily to affect local temperatures suggesting that
the first order transient climate response of the system is determined by feedback processes and only secondarily by the local
pattern of radiative forcing. The warming is accompanied by a more active hydrological cycle with increases in precipitation
and evaporation rates that are delayed by comparison with temperature increases. There is an “El Nino-like” shift in precipitation
and an overall increase in the interannual variability of precipitation. The effect of the aerosol forcing is again primarily
to delay and counteract the GHG-induced increase. Decreases in soil moisture are common but regionally dependent and interannual
variability changes show considerable structure. Snow cover and sea-ice retreat. A PNA-like anomaly in mean sea-level pressure
with an enhanced Aleutian low in northern winter is associated with the tropical shift in precipitation regime. The interannual
variability of mean sea-level pressure generally decreases with largest decreases in the tropical Indian ocean region. Changes
to the ocean thermal structure are associated with a spin-down of the Atlantic thermohaline circulation together with a decrease
in its variability. The effect of aerosol forcing, although modest, differs from that for most other quantities in that it
does not act primarily to counteract the GHG forcing effect. The barotropic stream function in the ocean exhibits modest change
in the north Pacific but accelerating changes in much of the Southern Ocean and particularly in the north Atlantic where the
gyre spins down in conjunction with the decrease in the thermohaline circulation. The results differ in non-trivial ways from
earlier equilibrium 2 × CO2 results with the CCCma model as a consequence of the coupling to a fully three-dimensional ocean model and the evolving nature
of the forcing.
Received: 24 September 1998 / Accepted: 8 October 1999 相似文献
20.
L. G. Bell 《Theoretical and Applied Climatology》2002,73(3-4):243-247
Summary ?It is postulated that before the influence of glaciation, it was the amount of cloud cover and the thermal inertia of the
ocean that controlled the Earth’s temperature. The control system went into oscillation 37 myr BP when Antarctica started
moving into its present position, the temperature of the ocean and that of the rest of the environment opposing each other
in antisymmetric mode. Support for this theory is provided by the observation of periods of enhanced glaciation at regular
intervals. The enhancement, being attributed to harmonics with the Earth’s 22,000 yr-precession and 41,000 yr-nutation cycles,
allows the calculation of 23,500 yr for the period of the ocean/atmosphere-temperature cycle. The corresponding lag time between
atmosphere and ocean is 11,750 yr.
Received February 17, 2002; revised March 19, 2002; accepted April 9, 2002 相似文献