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1.
Statistical downscaling of hourly and daily climate scenarios for various meteorological variables in South-central Canada 总被引：1，自引：1，他引：0
Summary A regression-based methodology was used to downscale hourly and daily station-scale meteorological variables from outputs
of large-scale general circulation models (GCMs). Meteorological variables include air temperature, dew point, and west–east
and south–north wind velocities at the surface and three upper atmospheric levels (925, 850, and 500 hPa), as well as mean
sea-level air pressure and total cloud cover. Different regression methods were used to construct downscaling transfer functions
for different weather variables. Multiple stepwise regression analysis was used for all weather variables, except total cloud
cover. Cumulative logit regression was employed for analysis of cloud cover, since cloud cover is an ordered categorical data
format. For both regression procedures, to avoid multicollinearity between explanatory variables, principal components analysis
was used to convert inter-correlated weather variables into uncorrelated principal components that were used as predictors.
The results demonstrated that the downscaling method was able to capture the relationship between the premises and the response;
for example, most hourly downscaling transfer functions could explain over 95% of the total variance for several variables
(e.g. surface air temperature, dew point, and air pressure). Downscaling transfer functions were validated using a cross-validation
scheme, and it was concluded that the functions for all weather variables used in the study are reliable. Performance of the
downscaling method was also evaluated by comparing data distributions and extreme weather characteristics of downscaled GCM
historical runs and observations during the period 1961–2000. The results showed that data distributions of downscaled GCM
historical runs for all weather variables are significantly similar to those of observations. In addition, extreme characteristics
of the downscaled meteorological variables (e.g. temperature, dew point, air pressure, and total cloud cover) were examined.
Authors’ addresses: Chad Shouquan Cheng, Guilong Li, Qian Li, Atmospheric Science and Applications Unit, Meteorological Service
of Canada Branch-Ontario, Environment Canada, 4905 Dufferin Street, Toronto, Ontario, Canada M3H 5T4; Heather Auld, Adaptation
and Impacts Research Division, MSC Branch, Environment Canada, Toronto, Canada. 相似文献
2.
A comparison of two separate MM5 land-use datasets (i.e., ‘US Geological Survey (USGS)’ and ‘Pollutants in the Atmosphere and their Transport over Hong Kong (PATH)’, each with different parameter values and different spatial distributions) was performed to understand the importance of land-surface processes and land-atmosphere interactions in the evolution of mesoscale weather phenomena during a high pollution episode in Hong Kong from 28 December 1999 through 1 January 2000. Also, a series of high resolution mesoscale numerical experiments was performed to investigate the possible roles of various surface characteristics or land-use parameters in this high pollution episode. Specifically, the relative importance of six land-use parameters including the roughness length, thermal inertia, soil moisture availability, albedo, surface heat capacity and surface emissivity are studied. Results from this study suggest that the soil moisture availability is the most important controlling parameter on the flow pattern and on surface fluxes. Sensitivity tests also show that the general flow pattern is insensitive to the other five land-use parameters 相似文献
3.
Alvaro de la Cámara C. R. Mechoso K. Ide R. Walterscheid G. Schubert 《Climate Dynamics》2010,35(6):965-975
The present paper examines the vortex breakdown and large-scale stirring during the final warming of the Southern Hemisphere
stratosphere during the spring of 2005. A unique set of in situ observations collected by 27 superpressure balloons (SPBs)
is used. The balloons, which were launched from McMurdo, Antarctica, by the Stratéole/VORCORE project, drifted for several
weeks on two different isopycnic levels in the lower stratosphere. We describe balloon trajectories and compare them with
simulations obtained on the basis of the velocity field from the GEOS-5 and NCEP/NCAR reanalyses performed with and without
VORCORE data. To gain insight on the mechanisms responsible for the horizontal transport of air inside and outside the well-isolated
vortex we examine the balloon trajectories in the framework of the Lagrangian properties of the stratospheric flow. Coherent
structures of the flow are visualized by computing finite-time Lyapunov exponents (FTLE). A combination of isentropic analysis
and FTLE distributions reveals that air is stripped away from the vortex’s interior as stable manifolds eventually cross the
vortex’s edge. It is shown that two SPBs escaped from the vortex within high potential vorticity tongues that developed in
association with wave breaking at locations along the vortex’s edge where forward and backward FTLE maxima approximately intersect.
The trajectories of three SPBs flying as a group at the same isopycnic level are examined and their behavior is interpreted
in reference to the FTLE field. These results support the concept of stable and unstable manifolds governing transport of
air masses across the periphery of the stratospheric polar vortex. 相似文献
4.
5.
This paper contributes to the literature underscoring the importance of climatic variance by developing a framework for incorporating the means and tails of the distributions of rainfall and temperature into empirical models of agricultural production. The methodology is applied to estimate the impact of climate change on the discrete choice decision to adopt irrigation since it is an important adaptation to climate change. We develop a discrete choice model for the decision to install irrigation capacity that captures the effects of both climate means and extremes. Climatic means and frequencies of climatic events in the upper tails of the temperature and precipitation distributions are used to estimate the parameters of a normal distribution for temperature and a Weibull distribution for precipitation. Using estimates from a probit model, we examine the independent effects of changing climatic mean and variance on the probability of adopting irrigation. Increasing the mean temperature, holding variance constant, shifts the entire distribution toward warmer temperatures—increasing the frequency of extreme temperatures. For precipitation, the specification captures the separate effects of mean rainfall, frequency of rainfall, and frequency of extreme events. The results show that the tails of the temperature and precipitation distributions, not the means, are the dominant climatic determinants in irrigation adoption. The results also show that water availability, soil characteristics, farm size and operator demographics are important determinants of irrigation. 相似文献
6.
M. Mayers T. N. Krishnamurti C. Depradine L. Moseley 《Meteorology and Atmospheric Physics》2001,78(1-2):75-88
Summary
A month-long short-range numerical weather prediction experiment using the Florida State University’s (FSU) global and regional
models and the multi-model/multi-analysis super-ensemble over the Eastern Caribbean domain is presented in this paper. The
paper also investigates weather prediction capabilities of FSU global and regional models by examining the root mean square
errors (RMSE) for the wind and precipitation fields.
Super-ensemble forecasting, a new statistical approach to weather forecasting, is used over this domain. Here, forecasts from
a number of numerical models provide the input and statistical combinations of these forecasts produce the super-ensemble
forecast. A similar approach is used for the precipitation field where one model using different rain rate algorithms is used
to generate different model outputs.
The results show that the super-ensemble method produces forecasts that are superior to those obtained from the ensemble members.
Received May 29, 2000/Revised February 15, 2001 相似文献
7.
An empirical classification of weather types in the Mediterranean Basin and their interrelation with rainfall 总被引：1，自引：1，他引：0
T. Littmann 《Theoretical and Applied Climatology》2000,66(3-4):161-171
Summary This paper presents a classification of weather types in the Mediterranean Basin based on cluster analysis of the daily occurrences
of several surface pressure centers and the subjective identification of 500 hPa trough axis positions (1992–1996). The procedure
results in 20 types that explain 69% of overall pressure center variance and which are consistent with the seasonal succession
of regional circulation. The development of weather types in winter is primarily controlled by the eastward propagation of
barotropic waves while departures from the zonal flow pattern in summer tend to be linked to blocked stationary pools. H1-types
with anticyclonic circulation in the Western Mediterranean and cyclonic flow in the eastern part are well interrelated with
zonal and anticyclonic general weather types in Central Europe. H2-types featuring a weak Azores Anticyclone interrelate with
a variety of meridional circulation types after the Hess and Brezowski (1969) classification. The 20 types explain rainfall
variance in the core Mediterranean regions (as defined by principal components) to a high degree while rainfall variance in
marginal regions is influenced by circulation patterns not being typical for the Mediterranean Basin.
Received January 29, 1999 Revised March 28, 2000 相似文献
8.
Sea surface temperature (SST) and salinity (SSS) time series from four ocean weather stations and data from an integration
of the GFDL coupled ocean-atmosphere model are analyzed to test the applicability of local linear stochastic theory to the
mixed-layer ocean. According to this theory, mixed-layer variability away from coasts and fronts can be explained as a ‘red
noise’ response to the ‘white noise’ forcing by atmospheric disturbances. At one weather station, Papa (northeast Pacific),
this stochastic theory can be applied to both salinity and temperature, explaining the relative redness of the SSS spectrum.
Similar results hold for a model grid point adjacent to Papa, where the relationships between atmospheric energy and water
fluxes and actual changes in SST and SSS are what is expected from local linear stochastic theory. At the other weather stations,
this theory cannot adequately explain mixed-layer variability. Two oceanic processes must be taken into account: at Panulirus
(near Bermuda), mososcale eddies enhance the observed variability at high frequencies. At Mike and India (North Atlantic),
variations in SST and SSS advection, indicated by the coherence and equal persistence of SST and SSS anomalies, contribute
to much of the low frequency variability in the model and observations. To achieve a global perspective, TOPEX altimeter data
and model results are used to identify regions of the ocean where these mechanisms of variability are important. Where mesoscale
eddies are as energetic as at Panulirus, indicated by the TOPEX global distribution of sea level variability, one would expect
enhanced variability on short time scales. In regions exhibiting signatures of variability similar to Mike and India, variations
in SST and SSS advection should dominate at low frequencies. According to the model, this mode of variability is found in
the circumpolar ocean and the northern North Atlantic, where it is associated with the irregular oscillations of the model’s
thermohaline circulation.
Received: 11 March 1996 / Accepted: 6 September 1996 相似文献
9.
10.
A. Mazzarella 《Theoretical and Applied Climatology》2007,88(3-4):193-199
Summary Spectral analysis of geomagnetic activity, global air temperature, Earth’s rotation rate and zonal circulation, when smoothed
from secular trend and periods shorter than 23 years, shows a concentration of energy around the 60-year period explaining
more than 80% of the entire variance. This information has enabled the set-up of a cascade physical model that integrates
the Sun-atmosphere-Earth system as a single unit and ties solar corpuscular radiation to global warming through Earth’s rotation
and atmospheric circulation. Our results suggest that changes in geomagnetic activity, and in the Earth’s rotation, could
be used as long- and short-term indicators, respectively, of future changes in global air temperature. 相似文献
11.
T. Klein G. Heinemann D. H. Bromwich J. J. Cassano K. M. Hines 《Meteorology and Atmospheric Physics》2001,78(1-2):115-132
Summary
Simulations of the katabatic wind system over the Greenland ice sheet for the two months April and May 1997 were performed
using the Norwegian Limited Area Model (NORLAM) with a horizontal resolution of 25 km. The model results are intercompared
and validated against observational data from automatic weather stations (AWS), global atmospheric analyses and instrumented
aircraft observations of individual cases during that period. The NORLAM is able to simulate the synoptic developments and
daily cycle of the katabatic wind system realistically. For most of the cases covered by aircraft observations, the model
results agree very well with the measured developments and structures of the katabatic wind system in the lowest 400 m. Despite
NORLAM’s general ability of reproducing the four-dimensional structure of the katabatic wind, problems occur in cases, when
the synoptic background is not well captured by the analyses used as initial and boundary conditions for the model runs or
where NORLAM fails to correctly predict the synoptic development. The katabatic wind intensity in the stable boundary layer
is underestimated by the model in cases when the simulated synoptic forcing is too weak. An additional problem becomes obvious
in cases when the model simulates clouds in contrast to the observations or when the simulated clouds are too thick compared
to the observed cloud cover. In these cases, the excessive cloud amount prevents development of the katabatic wind in the
model.
Received September 22, 2000/Revised March 16, 2001 相似文献
12.
T. Ben-Gai A. Bitan A. Manes P. Alpert A. Israeli 《Theoretical and Applied Climatology》1998,61(3-4):207-215
Summary Recent studies imply that significant climatic changes over the central and southern coastal plain in Israel may be due to
changes in land usage, which have taken place since the National Water Carrier operation in the early 1960’s. Such changes
are reflected in the spatial distribution of the surface albedo pattern, obviously resulting in changes in the surface radiation
balance and, subsequently, modifying the surface heat fluxes and the stability conditions of the Planetary Boundary Layer
(PBL).
An Eppley PSP Pyranometer facing downward was mounted on a small Cessna aircraft and flown along the coastal plain from Tel
Aviv to the northern Negev south of Beer Sheva, at an altitude of approximately 500 feet, measuring surface reflection. The
incoming solar radiation was measured simultaneously, at several surface radiation stations of the Israel Meteorological Service,
along the flight path. The results show large differences in surface reflection distributions, between the cultivated areas
in southern Israel (as low as 0.15), and the adjacent arid regions (with values of up to 0.35). Historical albedo maps were
reconstructed according to land utilization maps of the 1930’s and the 1960’s. A comparison between recent albedo map and
the reconstructed maps, indicates temporal changes in the surface albedo pattern during the last decades.
Received January 15, 1998 Revised June 23, 1998 相似文献
13.
Juan Carlos Bergmann 《Boundary-Layer Meteorology》2006,119(1):171-179
Precision measurements indicate that the stability capping of the neutral planetary boundary layer (PBL) that leads to a reduced
PBL height is caused by the very stable upper part of the PBL, rather than by an overlying inversion. Radiative processes
related to liquid water in boundary-layer clouds seem to play the key role for the formation of the stable upper PBL. The
famous Leipzig Profile – generally considered as an example of a neutral PBL – has been included in Hess’s analysis because
its PBL height is considerably lower than the ca. 3000 m to be expected by numerical models in truly neutral conditions. An
analysis of the original observations reveals that the Leipzig PBL was stable and that it can be consistently treated as a
‘normal’ stable PBL with a height of ca. 700 m. A further finding is that the super-geostrophic PBL wind speed maxima predicted
by almost all models are not observed in near-steady-state conditions. For the ‘ranking’ of analytical models versus numerical
models, the comparisons with measurements show that the analytical models perform comparably well and even partially better
than the numerical models. 相似文献
14.
Catastrophic winter storms: An escalating problem 总被引：2，自引：0，他引：2
Stanley A. Changnon 《Climatic change》2007,84(2):131-139
Winter storms are a major weather problem in the USA and their losses have been rapidly increasing. A total of 202 catastrophic
winter storms, each causing more than $1 million in damages, occurred during 1949–2003, and their losses totaled $35.2 billion
(2003 dollars). Catastrophic winter storms occurred in most parts of the contiguous USA, but were concentrated in the eastern
half of the nation where 88% of all storm losses occurred. They were most frequent in the Northeast climate district (95 storms),
and were least frequent in the West district (14 catastrophic storms). The annual average number of storms is 3.7 with a 1-year
high of 9 storms, and 1 year had no storms. Temporal distributions of storms and their losses exhibited considerable spatial
variability across the nation. For example, when storms were very frequent in the Northeast, they were infrequent elsewhere,
a result of spatial differences in storm-producing synoptic weather conditions over time. The time distribution of the nation’s
202 storms during 1949–2003 had a sizable downward trend, whereas the nation’s storm losses had a major upward trend for the
55-year period. This increase over time in losses, given the decrease in storm incidences, was a result of significant temporal
increases in storm sizes and storm intensities. Increases in storm intensities were small in the northern sections of the
nation, but doubled across the southern two-thirds of the nation, reflecting a climatic shift in conditions producing intense
winter storms. 相似文献
15.
Summary The annual occurrence of different weather types of Schüepp’s synoptic classification in the Alpine region has significantly
changed since the beginning of its recording in 1945. The annual frequency (number of days per year) has shifted towards more
convective and less advective weather types. Since 1945 the number of long-lasting convective episodes rose and the number
of long-lasting advective episodes lessened. Most of these changes took place in winter. The annual frequencies of weather
types and the annual mean of certain local meteorological parameters are significantly correlated. On the large scale there
is a strong interdependence between the high pressure weather type and the North Atlantic Oscillation (NAO) index which is
based on the sea-level pressure difference between Portugal and Iceland.
Received July 28, 1997 Revised November 18, 1997 相似文献
16.
It is discussed that the anomaly in long-range weather is due to the stable sustained circulation.Waveson monthly or seasonal departure maps can essentially be regarded as probability waves which reflectthe anomaly distribution of heat sources and sinks on the earth's surface.The persistent stable circulationcreats these distributions which serve as persistent disturbance sources and in turn feedback the generalcirculation with persistent stability in later period.The departure probability waves on a six-month (September—February)chart reflect the anomalous dis-tribution of heat sources and sinks on the underlying surface.The waves north of 30°N move slowly andeastward on the Eurasian Continent against the temperature gradient,while they are stationary south of 30°N.A statistical model is developed to predict the spring—summer temperature and precipitation of next yearby using the six-month departure probability wave of last year.During 1982--1985 it was tested in severalprovinces of northern China with encousaging results. 相似文献
17.
The ability of Māori to understand, record and forecast weather and climate has been an important factor in successfully responding
to past weather and climatic change in New Zealand. Through interacting with local environments over the centuries Māori have
developed a wealth of environmental knowledge, with the lessons learnt having been incorporated into traditional and modern
practices of agriculture, fishing, medicine, education and conservation. In partnership with the tribal group Te Whānau-ā-Apanui,
NIWA’s Māori Research and Development Unit (Te Kuwaha o Taihoro Nukurangi) have initiated a pilot project to identify and
document Māori environmental knowledge (MEK) of weather and climate in New Zealand. Using a Kaupapa Māori based research approach
and semi-directive interviewing, an intimate understanding of local weather and climate was demonstrated by elders from Te
Whānau-ā-Apanui. This knowledge includes the use of a vast indigenous nomenclature for local weather and climate phenomenon,
the oral recording of weather and climate based events and trends, and the identification of environmental indicators to forecast
weather and climate. Learning from this knowledge provides an opportunity to understand what has helped Māori adapt to weather
and climate variability in the past. It also provides clues on how to enhance present day Māori and western scientific understanding
of local weather and climate in New Zealand.
An erratum to this article can be found at 相似文献
18.
Modelling Wet and Dry Spells with Mixture Distributions 总被引：1，自引：0，他引：1
Summary The object of the study is to develop a discrete precipitation model which is able to simulate local, daily series of precipitation
occurrences. The model is fitted to the observed data of two stations, Szeged and Szombathely, in Hungary (1951–1995), with
pronounced attention to the reproduction of long dry periods, as characteristic features of the climate in Central Europe.
The point of the approach is to model the duration of consecutive dry and wet series, i.e., spells, instead of individual
wet or dry days. After having comparisons of three different aspects performed, the selected precipitation threshold is 0.1 mm.
This threshold keeps the duration of dry and wet periods more or less balanced, whereas the value of the threshold does not
fundamentally influence either the conditional distribution of macrocirculation types or the local weather statistics related
to the so defined wet or dry days. The duration of both wet and dry spells are found to be independent of the length of either
the preceding (opposite) or the last, but one (identical) state. It is also demonstrated that mixed distributions fairly fit
to the wet and dry spells, whereas the simple geometric does not, especially due to the erroneous lack of long dry sequences.
Weighted sum of two geometric distributions, as well as that of one geometric and one Poisson distribution exhibits good fitting
for the dry spells, whereas only the latter one can be advised to employ for the wet periods. Parameters of the distributions
obviously depend on the season and the site, in question.
Received June 30, 1999 Revised February 3, 2000 相似文献
19.
本文首先讨论了造成长期异常天气的原因:主要是由于环流的持续稳定。指出月、季距平图上所反映的波动实质上是几率波动,它反映了下垫面冷热源(包括:雪盖、海冰、海温等)的异常分布。从而得出持续稳定的环流造成了下垫面冷热源的异常,而下垫面冷热源的异常分布作为一个持久性的扰动源对大气又起反馈作用,又造成了在某些特定地区环流的持续稳定,这样又形成了后期冷热源异常的再分布。 六个月距平几率波主要是反映下垫面冷热源的异常分布。它的变化是十分缓慢的。在30°N以南几乎呈静止状态,而30°N以北的几率波在欧亚大陆多数情况下是缓慢东进的。它的运动方向与下垫面的温度梯度相反。 最后利用半年时间尺度的距平几率波的特性,提出一种利用前一年秋到冬季的距平几率波预报次年春到夏季的降水、气温统计模型。经河北、内蒙、辽宁、吉林等省、区某些气象台1982—1985年的实地试用,反映较好,一致认为预报准确率比较稳定。 相似文献
20.
This article proposes and tests a model of the causes and consequences of Americans’ judgments of the national seriousness of global warming. The model proposes that seriousness judgments about global warming are a function of beliefs about the existence of global warming, attitudes toward it, the certainty with which these beliefs and attitudes are held, and beliefs about human responsibility for causing global warming and people’s ability to remedy it. The model also proposes that beliefs about whether global warming is a problem are a function of relevant personal experiences (with the weather) and messages from informants (in this case, scientists), that attitudes toward global warming are a function of particular perceived consequences of global warming, and that certainty about these attitudes and beliefs is a function of knowledge and prior thought. Data from two representative sample surveys offer support for all of these propositions, document effects of national seriousness judgments on support for ameliorative efforts generally and specific ameliorative policies, and thereby point to psychological mechanisms that may be responsible for institutional and elite impact on the public’s assessments of national problem importance and on public policy preferences. 相似文献