Showing papers in "Advances in Atmospheric Sciences in 2001"
TL;DR: The transition of the global atmospheric circulation in the end of 1970's can clearly be detected in the atmospheric temperature, wind velocity, and so on as mentioned in this paper, and wavelet analysis reveals that the temporal scale of this change is larger than 20 years.
Abstract: The transition of the global atmospheric circulation in the end of 1970's can clearly be detected in the atmospheric temperature, wind velocity, and so on. Wavelet analysis reveals that the temporal scale of this change is larger than 20 years. Studies in this work indicate that the trend of the transition over the mid-latitude Asia is opposite to that of global average for some variables at the middle troposphere. Another finding of this research is that the African-Asian monsoon circulation is weaker and the trade wind over the tropical eastern Pacific is weaker as well after this transition. Such a signal may be found in the summer precipitation over China as well.
533 citations
TL;DR: In this article, the authors investigated the impacts of greenhouse effects (2 × CO2) upon climate change over China as simulated by a regional climate model over China (RegCM / China).
Abstract: Impacts of greenhouse effects (2 × CO2) upon climate change over China as simulated by a regional climate model over China (RegCM / China) have been investigated. The model was based on RegCM2 and was nested to a global coupled ocean-atmosphere model (CSIRO R21L9 AOGCM model). Results of the control run (1 × CO2) indicated that simulations of surface air temperature and precipitation in China by RegCM are much better than that by the global coupled model because of a higher resolution. Results of sensitive experiment by RegCM with 2 × CO2 showed that the surface air temperature over China might increase remarkably due to greenhouse effect, especially in winter season and in North China. Precipitation might also increase in most parts of China due to the CO2 doubling.
185 citations
TL;DR: In this paper, a diagnostic study was made to investigate the relationship between water vapor transport from Indian monsoon and that over East Asia in Northern summer, and it was found that water vapor transfer from Indian Monsoon is inverse to that over east Asia.
Abstract: A diagnostic study is made to investigate the relationship between water vapor transport from Indian
monsoon and that over East Asia in Northern summer. It is found that water vapor transport from Indian
monsoon is inverse to that over East Asia. More (less) Indian monsoon water vapor transport corresponds
to less (more) water vapor transport over East Asia and less (more) rainfall in the middle and lower reaches
of the Yangtze River valley. The Indian summer monsoon water vapor transport is closely related to the in
tensity of the western Pacific subtropical high in its southwestern part. The stronger (weaker) the Indian sum
mer monsoon water vapor transport, the weaker (stronger) the western Pacific subtropical high in its
southwestern part, which leads to less (more) water vapor transport to East Asia, and thus less (more) rain
fall in the middle and lower reaches of the Yangtze River valley. Analysis of the out-going longwave radia
tion anomalies suggests that the convective heating anomalies over the Indian Ocean may have significant
impact not only on the Indian monsoon, but also on the East Asian monsoon.
171 citations
TL;DR: Based on the 1961-1995 atmospheric apparent heat source/ sink and the 1961−1990 snow-cover days and depth over the Qinghai-Xizang Plateau (QXP), the authors discusses the interannual variability of the heat regime and its relation to atmospheric circulation.
Abstract: Based on the 1961–1995 atmospheric apparent heat source/ sink and the 1961–1990 snow-cover days and depth over the Qinghai-Xizang Plateau (QXP) and the 1961–1995 reanalysis data of NCEP/ NCAR and the 1975–1994 OLR data, this paper discusses the interannual variability of the heat regime and its relation to atmospheric circulation. It is shown that the interannual variability is pronounced, with maximal variability in spring and autumn, and the variability is heterogeneous horizontally. In the years with the weak (or strong) winter cold source, the deep trough over East Asia is to the east (or west) of its normal, which corresponds to strong (or weak) winter monsoon in East Asia. In the years with the strong (or weak) summer heat source, there exists an anomalous cyclone (or anticyclone) in the middle and lower troposphere over the QXP and its neighborhood and anomalous southwest (or northeast) winds over the Yangtze River valley of China, corresponding to strong (or weak) summer monsoon in East Asia. The summer heat source of the QXP is related to the intensity and position of the South Asia high. The QXP snow cover condition of April has a close relation to the heating intensity of summer. There is a remarkable negative correlation between the summer heat source of the QXP and the convection over the southeastern QXP, the Bay of Bengal, the Indo—China Peninsula, the southeastern Asia, the southwest part of China and the lower reaches of the Yangtze River and in the area from the Yellow Sea of China to the Sea of Japan.
83 citations
TL;DR: In this article, the SST variation in the equatorial Indian Ocean is studied with special interest in analyzing its dipole oscillation feature, and the amplitude of the positive phase is larger than the negative phase.
Abstract: The SST variation in the equatorial Indian Ocean is studied with special interest in analyzing its dipole oscillation feature. The dipole oscillation appears to be stronger in September-November and weaker in January-April with higher SST in the west region and lower SST in the east region as the positive phase and higher SST in the east region and lower SST in the west region as the negative phase. Generally, the amplitude of the positive phase is larger than the negative phase. The interannual variation (4-5 year period) and the interdecadal variation (25-30 year period) also exist in the dipole. The analyses also showed the significant impact of the Indian Ocean dipole on the Asian monsoon activity, because the lower tropospheric wind fields over the Southern Asia, the Tibetan high in the upper troposphere and the subtropical high over the northwestern Pacific are all related to the Indian Ocean dipole. On the other, the Indian Ocean dipole still has significant impact on atmospheric circulation and climate in North America and the southern Indian Ocean region (including Australia and South Africa).
77 citations
TL;DR: This paper describes a modified version of SSIB through implementing a new snow model (SAST) in Simplified Simple Biosphere Model SSIB for climate study and presents the evaluation results by testing the scheme based on the field data from Russia and France, indicating that the scheme developed here is workable and can be extended forClimate study.
Abstract: This paper describes a modified version of SSIB through implementing a new snow model (SAST) in Simplified Simple Biosphere Model SSIB for climate study and presents the evaluation results by testing the scheme based on the field data from Russia and France. The relevant equations in the scheme are given, which describe complicated interactive processes among air-vegetation-snow-soil continuum through mass and heat exchange. An efficient numerical scheme is developed to solve the nonlinear equations successfully. By using the field data from Russia and France, the function of the new scheme is evaluated. The numerical results from the scheme show good agreement with field data. It indicates that the scheme developed here is workable and can be extended for climate study.
55 citations
TL;DR: In this article, the authors investigated the effect of convective parameterization on the temporal characteristics of large-scale circulation and clouds and showed that the convective parameters have a strong impact on the time complexity of the convection and clouds.
Abstract: This study investigates the interaction between convection, clouds, and the large-scale circulation. By examining the sensitivity of the large-scale fields to a modification of the convective parameterization scheme in the NCAR CCM3, we show that the convective parameterization has a strong impact on the temporal characteristics of the large-scale circulation and clouds. When Convective Available Potential Energy (CAPE) in the atmosphere is used to close the convective parameterization, the simulated convection is continuous, and lacks the observed intermittence. When the CAPE change due to the large-scale forcing in the free troposphere is used, the simulated temporal behavior of convection is in much better agreement with the observations. We attribute this improvement to the enhanced coupling between convection and the large-scale forcing in the convective parameterization.
52 citations
TL;DR: The East Asian summer monsoon (EASM) underwent an interdecadal variation with interannual varia-tions during the period from 1958 to 1997, its index tended to decline from a higher stage in the mid-1960s until it reached a lower stage after 1980s as discussed by the authors.
Abstract: The East Asian summer monsoon (EASM) underwent an interdecadal variation with interannual varia-tions during the period from 1958 to 1997, its index tended to decline from a higher stage in the mid-1960’s until it reached a lower stage after 1980’s . Correlation analysis reveals that EASM is closely related with the global atmospheric circulation and sea surface temperature (SST). The differences between the weak and strong stage of EASM shows that, the summer monsoon circulation over East Asia and North Africa is sharply weakened, in the meantime, the westerlies in high latitudes and the trade-wind over the tropical ocean are also changed significantly. Over the most regions south of the northern subtropics, both air tem-perature in the lower troposphere and SST tended to rise compared with the strong stage of EASM. It is also revealed that the ocean-atmosphere interaction over the western Pacific and Indian Ocean plays a key role in interannual to interdecadal variation of EASM, most probably, the subtropical Indian Ocean is more im-portant. On the other hand, the ENSO event is less related to EASM at least during the concerned period.
51 citations
TL;DR: In this article, the relationship between summer rainfall over the east part of China and the East-Asian Summer Monsoon (EASM) was studied based on the summer rainfall grade data set from 1470 to 1999 and the rain gauge data set for the period of 1871-2000.
Abstract: Relationship between summer rainfall over the east part of China and East-Asian Summer Monsoon (EASM) was studied based on the summer rainfall grade data set from 1470 to 1999 and the rain gauge data set from 1951 to 1999 over the east part of China, and sea level pressure (SLP) data for the period of 1871–2000. A distinct 80a-oscillation of summer rainfall was found over North China (NC), southern part of Northeast China, over the middle and lower reaches of the Yangtze River (YR) and South China (SC). The 80a oscillation of summer rainfall over NC was varied in phase with that over SC, and was out of phase to that along the middle and lower reaches of the Yangtze River. Summer rainfall over NC correlated negatively with the SLP averaged for the area from 105’E to 120’E, and from 30’N to 35’N, but positively to that for the area from 120’E to !30’E, and from 20’N to 25’N. Therefore, an index of EASM was defined by the difference of averaged SLP over the two regions. The summer rainfall over NC was greater than normal when the EASM was strong, and while drought occurred along the middle and lower reaches of the Yangtze River. The drought was found over NC, and flood along the middle and lower reaches of the Yangtze River when the EASM was close to normal. Finally, the interdecadal variability of EASM was studied by using of long term summer rainfall grade data set over NC for the past 530 years.
50 citations
TL;DR: Based on the data from International Satellite Cloud Climatology Project (ISCCP) and Earth Radiation Budget Experiment (ERBE), the climatic cloud properties and cloud radiative forcing in the eastern China and the Indian monsoon region are compared as discussed by the authors.
Abstract: Based on the data from International Satellite Cloud Climatology Project (ISCCP) and Earth Radiation Budget Experiment (ERBE), the climatic cloud properties and cloud radiative forcing in the eastern China and the Indian monsoon region are compared. Although both of the Indian monsoon region and the eastern China are included in the Asian monsoon region and the seasonal cycles of rainfall are in phase, the properties of clouds and related cloud radiative forcing are significantly different. All of cloud components in the Indian region have similar phase structure of seasonal cycle. The maximum cloud fractions occur in the summer monsoon period and high clouds dominate the total cloud fraction. However, the seasonal features of clouds in the eastern China are complex. It is the mid-low clouds rather than high clouds dominating the total cloud fraction. The maximum total cloud fraction occurs in spring season. The total cloud and mid-low cloud fractions in winter season are larger than that in summer season. A unique global distinction of clouds in the eastern China is the largest cover of nimbostratus clouds. Reflecting to the cloud properties, the maximums of negative short wave, positive long wave and negative net cloud radiative forcing in the Indian monsoon region are in the summer season. In the eastern China, large negative short wave cloud radiative forcing occurs in early summer. The annual mean negative net cloud radiative forcing in the eastern China is obviously larger than that in the Indian region.
49 citations
TL;DR: In this article, a unified ENSO oscillator was proposed, which combines the positive and negative ocean-atmosphere feedbacks associated with the delayed oscillator, the western Pacific oscillator and the recharge-discharge oscillator.
Abstract: The El Nino-Southern Oscillation (ENSO) is an interannual phenomenon involved in the tropical Pacific Ocean-atmosphere interactions. The oscillatory nature of ENSO requires both positive and negative ocean-atmosphere feedbacks. The positive feedback is dated back to Bjerknes' hypothesis in the 1960s, and different negative feedbacks have been proposed since the 1980s associated with the delayed oscillator, the western Pacific oscillator, the recharge-discharge oscillator, and the advective-reflective oscillator. The delayed oscillator assumes that wave reflection at the western boundary provides a negative feedback for the coupled system to oscillate. The western Pacific oscillator emphasizes equatorial wind in the western Pacific that provides a negative feedback for the coupled system. The recharge-discharge oscillator argues that discharge and recharge of equatorial heat content cause the coupled system to oscillate. The advective-reflective oscillator emphasizes the importance of zonal advection associated with wave reflection at both the western and eastern boundaries. All of these physics are summarized in a unified ENSO oscillator. The delayed oscillator, the western Pacific oscillator, the recharge-discharge oscillator, and the advective-reflective oscillator can be extracted as special cases of the unified oscillator. As suggested by this unified oscillator, all of the previous ENSO oscillator mechanisms may be operating in nature.
TL;DR: In this article, a new oceanic general circulation model in pressure coordinates is formulated, and the numerical solution of the model is based on an energyconservation scheme of finite difference.
Abstract: A new oceanic general circulation model in pressure coordinates is formulated. Since the bottom pressure changes with time, the vertical coordinate is actually a pressure-σ coordinate. The numerical solution of the model is based on an energy—conservation scheme of finite difference. The most important new feature of the model is that it is a truly compressible ocean model and it is free of the Boussinesq approximations. Thus, the new model is quite different from many existing models in the following ways: 1) the exact form of mass conservation, 2) the in—situ instantaneous pressure and the UNESCO equation of state to calculate density, 3) the in—situ density in the momentum equations, 4) finite difference schemes that conserve the total energy. Initial tests showed that the model code runs smoothly, and it is quite stable. The quasi—steady circulation patterns generated by the new model compare well with existing models, but the time evolution of the new model seems different from some existing models. Thus, the non—Boussinesq models may provide more accurate information for climate study and satellite observations.
TL;DR: In this article, the authors analyzed inhomogeneities in the temperature series from Beijing and Shanghai, using the detailed histories of both sets of observations, and deduced from the daily observations and trends in the adjusted and unadjusted series are compared.
Abstract: Inhomogeneities in the temperature series from Beijing and Shanghai are analyzed, using the detailed histories of both sets of observations. The major corrections for different periods range from −0.33 to 0.6°C for Beijing and −0.33 to 0.3°C for Shanghai, Annual mean and extreme temperature series are deduced from the daily observations and trends in the adjusted and unadjusted series are compared. The adjusted yearly mean temperatures show a warming trend of 0.5°C/ century since the turn of this century and an enhanced one of 2.0°C/ century since the 1960s. In contrast, the unadjusted data show a twice this value trend for Shanghai but little trend for Beijing at the long-term scale and overestimate the recent warming by 50%–130%. Beijing experienced a decrease of frequency of the extremes together with a cooling during the 1940s–1970s and an increase of frequency of extremes together with a warming since then. The trends of frequency of extremes at Shanghai were more or less opposite. It is implied that the regional trends of strong weather variations may be different even when the regional mean temperatures coherently change.
TL;DR: Based on the data analyses by using NCEP/NCAR reanalysis data and other data (OLR, precipita-tion and temperature), it is shown that the tropospheric circulation and climate in East Asia and the northwestern Pacific region have the evident quasi-biennial oscillation (TBO) feature as discussed by the authors.
Abstract: Based on the data analyses by using NCEP/ NCAR reanalysis data and other data (OLR, precipita-tion and temperature), it is shown that the tropospheric circulation and climate in East Asia and the northwestern Pacific region have the evident quasi-biennial oscillation (TBO) feature It is also shown that anomalous East Asian winter monsoon can impact the atmospheric circulation and climate variations in the following summer, particularly in East Asian region; there is clear interaction between anomalous East Asian winter monsoon and ENSO cycle The continuous strong (weak) East Asian winter monsoon can ex-cite El Nino (La Nina) through the air-sea interaction, the El Nino (La Nina) event can lead the East Asian winter monsoon to be weak (strong) through the teleconnections or remote responses The strong or weak winter monsoon and ENSO cycle are linked each other It can be suggested that interaction between anoma-lous East Asian winter monsoon and ENSO cycle is a fundamental origin of the TBO
TL;DR: In this article, the authors performed a wavelet analysis of the mid and low-latitude circulation index at 850 hPa over East Asia, the East Asian monsoon index and the precipitation over the middle and lower reaches of the Yangtze River during 1998 South China Sea Monsoon Experiment (SCSMEX) from May to August.
Abstract: The wavelet analysis is performed of the mid- and low-latitude circulation index at 850 hPa over East Asia, the East Asian monsoon index and the precipitation over the middle and lower reaches of the Yangtze River during 1998 South China Sea Monsoon Experiment (SCSMEX) from May to August. Analysis shows that distinct 30–60 day low-frequency oscillation (LFO) exists in all of the above elements during the exper-iment period. Analysis of low-frequency wind field at 850 hPa from May to August with 5 days interval is performed in this paper. Analysis results reveal that: (1) A low-frequency monsoon circulation system over East Asia, characterized by distinct 30–60 day low-frequency oscillation, exists over 100°-150°E of East Asian area from the middle and eastern parts of China continent and the South China Sea to the western Pacific in both the Northern and Southern Hemisphere. The activity of East Asian monsoon is mainly af-fected by the low-frequency systems in it; (2) All of the tropical monsoon onset over the South China Sea in the fifth pentad of May, the beginning of the Meiyu period and heavy rainfall over the middle and lower reaches of the Yangtze River in mid-June and the heavy rainfall after mid-July are related to the activity of low-frequency cyclone belt over the region, whereas the torrential rainfall over the upper reaches of the Yangtze River in August is associated with the westward propagation of low-frequency anticyclone into the mainland; (3) There are two sources of low-frequency oscillation system over East Asia during SCSMEX. i.e. the equatorial South China Sea (SCS) and mid-high latitudes of the middle Pacific in the Northern Hemisphere. The low-frequency system over SCS propagates northward while that in mid-high latitudes mainly propagates from northeast to southwest. Both of the heavy rainfall over the middle and lower reaches of the Yangtze River in June and July are associated with the northward propagation of the above-mentioned SCS low-frequency systems from the tropical region and the southwestward propagation from mid-high latitudes respectively and their convergence in the middle and lower reaches of the Yangtze River; (4) There are two activities of low-frequency cyclone and anticyclone belt each in the East Asian monsoon system during May to August. However the activity of these low-frequency circulation systems is not clearly relevant to the low-frequency circulation system in the Indian monsoon system. This means that the low-frequency circulation systems in Indian monsoon and East Asian monsoon are independent of each other. The concept previously put forward by Chinese scholars that the East Asian monsoon circulation sys-tem (EAMCS) is relatively independent monsoon circulation system is testified once more in the summer 1998.
TL;DR: The circulation pattern corresponding to the strong / weak summer monsoon in the South China Sea (SCS) region and associated characteristics of the abnormal rainfall in Eastern China have been studied by using the NECP reanalysis data and precipitation data in China as discussed by the authors.
Abstract: The circulation pattern corresponding to the strong / weak summer monsoon in the South China Sea (SCS) region and the associated characteristics of the abnormal rainfall in Eastern China have been studied by using the NECP reanalysis data and precipitation data in China. The results show that the climate variations in China caused by the strong / weak summer monsoon are completely different (even in opposite phase). The analyses of atmospheric intraseasonal oscillation (ISO) activity showed that the atmospheric ISO at 850 hPa near the SCS region is strong (weak) corresponding to the strong (weak) SCS summer monsoon. And the analyses of the circulation pattern of the atmospheric ISO showed that the strong / weak SCS summer monsoon circulation (200 hPa and 850 hPa) result mainly from abnormal atmospheric ISO.
TL;DR: In this article, the characteristics of aerosols, the effects on climate, and dust aerosol research are reviewed, and the important fields and trends of atmospheric aerosol researches in the near future are discussed.
Abstract: In recent years, the Chinese scientists have undertaken numerous researches on aerosol, and made many achievements. This paper reviews the above researches on aerosols which mainly focus on the follow-ing three aspects: the characteristics of aerosols, the effects on climate, and dust aerosol research. Present in-ternational research plans in relation to aerosols are briefly introduced. The important fields and trends of atmospheric aerosol researches in the near future are also pointed out and discussed.
TL;DR: In this paper, the vertical circulation structure of the western Pacific subtropical high (STH) and its interannual variation features in relation to the SE monsoon and external thermal forcing were investigated.
Abstract: The paper investigates the vertical circulation structure of the western Pacific subtropical high (STH) and its interannual variation features in relation to East Asian subtropical summer monsoon and external thermal forcing by using the high-resolution and good-quality observations from the 1998 South China Sea Summer Monsoon Experiment (SCSMEX), the NCEP 40-year reanalysis data and relevant SST and the STH parameters. It is found that the vertical circulation structures differ greatly in features between quasi-stationary and transient components of the western Pacific STH. When rainstorms happen in the rainband of East Asian subtropical monsoon on the STH north side, the downdrafts are distinct around the ridge at a related meridian. The sinking at high (low) levels comes from the north (south) side of the STH, thereby revealing that the high is a tie between tropical and extratropical systems. The analyses of this paper suggest that the latent heat release associated with subtropical monsoon precipitation, the offshore SST and East Asian land-sea thermal contrast have a significant effect on the STH interannual anomaly. Our numer-ical experiment shows that the offshore SSTA-caused sensible heating may excite an anomalous anticyclonic circulation on the west side, which affects the intensity (area) and meridional position of the western Pacific STH.
TL;DR: In this article, the authors investigated the correlation between the mid-eastern China summer monsoon rainfalls (MECSMRs) and the global sea surface temperatures (SSTs), with SST leading to rain-fall.
Abstract: Some features associated with Eastern China Precipitation (ECP), in terms of mean climatology, sea-sonal cycle, interannual variability are studied based on monthly rainfall data. The rainfall behavior over Eastern China has fine spatial structure in the seasonal variation and interannual variability. The revealed characteristics of ECP motivate us dividing Eastern China into four sub—regions to quantify significant lag—correlations of the rainfalls with global sea surface temperatures (SSTs) and to study the ocean’s pre-dominant role in forcing the eastern China summer monsoon rainfalls. Lagged correlations between the mid—eastern China summer monsoon rainfalls (MECSMRs) and the global SSTs, with SST leading to rain-fall, are investigated. The most important key SST regions and leading times, in which SSTs are highly corre-lated with the MECSMRs, are selected. Part of the results confirms previous studies that show links between the MECSMRs and SSTs in the eastern equatorial Pacific associated with the El Nino — Southern Oscillation (ENSO) phenomenon. Other findings include the high lag correlations between the MECSMRs and the SSTs in the high and middle latitude Pacific Ocean and the Indian Ocean, even the SSTs over the Atlantic Ocean, with SST leading—time up to 4 years. Based on the selected SST regions, regression equa-tions are developed by using the SSTs in these regions in respective leading time. The correlation coefficient between the observed rainfalls and regressed rainfalls is over 0.85. The root mean square error (RMSE) for regressed rainfall is around 65% of the standard deviation and about 15% of the mean rainfall. The regression equation has also been evaluated in a forecasting mode by using independent data. Discussion on the consistence of the SST—rainfall correlation with circulation field is also presented.
TL;DR: In this article, the difference in atmospheric circulation and Sea Surface Temperatures (SSTs) between weak and strong convection over the tropical western Pacific warm pool (signified as WPWP) was examined.
Abstract: The difference is examined in atmospheric circulation and Sea Surface Temperatures (SSTs) in the trop-ics and subtropics between weak and strong convection over the tropical western Pacific warm pool (signified as WPWP). The WPWP is chosen as the region (110–160°E, 10–20°N), where the Outgoing Longwave Radiation (OLR) shows a great year-to-year variance. A composite study was carried out to examine the differences in atmospheric circulation and SSTs between weak and strong convection over WPWP. First, NCEP/NCAR re-analysis data and satellite-observed OLR data are used to examine the differences. ERA data, in which the OLR data are calculated, are then used for re-examination.
TL;DR: In this paper, the relationship between aerosol size distribution and relative humidity is discussed and the results show that the size distribution, diurnal variation, daily variation of atmospheric aerosols have a good relation to relative humidity and Richardson number.
Abstract: Number concentration and size distribution of atmospheric aerosols were measured in Beijing by an optical particle counter. The relationship between aerosol size distribution and relative humidity is discussed. The results show that the size distribution, diurnal variation, daily variation of atmospheric aerosols have a good relation to relative humidity and Richardson number.
TL;DR: In this article, two simulations, one for the control run and another for the perturbation run, with a global coupled ocean-atmosphere-land system model (IAP/LASG GOALS version 4) have been carried out to study the global warming, with much detailed emphasis on East Asia.
Abstract: Two simulations, one for the control run and another for the perturbation run, with a global coupled ocean—atmosphere—land system model (IAP/ LASG GOALS version 4) have been carried out to study the global warming, with much detailed emphasis on East Asia. Results indicate that there is no climate drift in the control run and at the time of CO2 doubling the global temperature increases about 1.65°C. The GOALS model is able to simulate the observed spatial distribution and annual cycles of temperature and precipitation for East Asia quite well. But, in general, the model underestimates temperature and overestimates rainfall amount for regional annual average. For the climate change in East Asia, the temperature and precipitation in East Asia increase 2.1°C and 5% respectively, and the maximum warming occurs at middle—latitude continent and the maximum precipitation increase occurs around 25°N with reduced precipitation in the tropical western Pacific.
TL;DR: In this article, the authors analyzed the annual cycle characteristics of the SSH in the South China Sea (SCS) based on the Sea Surface Height (SSH) anomaly data from the TOPEX / POSEIDON-ERS altimeter data and the Parallel Ocean Climate Model (POCM) prediction.
Abstract: The annual cycle characteristics of the SSH in the South China Sea (SCS) are analyzed based on the Sea Surface Height (SSH) anomaly data from the TOPEX / POSEIDON-ERS altimeter data and the Parallel Ocean Climate Model (POCM) prediction. The results show that the distributions of the SSH anomalies of the SCS in January, March and May, are opposite to those in July, September and November respectively; In January (July) there is the SSH negative (positive) anomaly in the deep water basin and at the Luzon Strait, while there is positive (negative) anomaly on the most of continental shelves in the west and south of South China Sea; In March (September) the SSH anomalies are similar to those in January (July), although their magnitudes have decreased and a small positive (negative) anomaly appears in the center of the South China Sea; The amplitude of the SSH annual cycle reaches its maximum in the Northwest of the Luzon Is-land; The seasonal variability of the wind stress is dominant in the formation of the SSH seasonal variability.
TL;DR: In this paper, a self-memorization equation of the atmospheric motion has been derived for decadal forecast by means of the thermodynamic equation and the precipitation equation, and the verification scores of the hindcasts of the model in the period from I to 12 years are much higher than that of monthly weather forecasts at present.
Abstract: In view of the fact that the atmospheric motion is an irreversible process, a memory function which can recall the observation data in the past is introduced, moreover, a special concept of self-memorization of the atmospheric motion is proposed, and a so-called self-memorization equation of the atmospheric motion has been derived. Based on the self-memorization principle, a numerical model for decadal forecast is established by means of the thermodynamic equation and the precipitation equation. The verification scores of the hindcasts of the model in the period from I to 12 years are much higher than that of monthly weather forecasts at present.
TL;DR: In this paper, the authors investigated the physical processes responsible for the prolonged maintenance of this key system in terms of internal forcing (transient eddy upon basic flow) and external forcing (tropical heating forcing) via diagnosis and numerical experiments.
Abstract: The 1998 summer—time floods at the Yangtze River basin of China, the severest in last 50 years or so, directly resulted from the abnormal extension of Meiyu (rainy season), which was related to a weak East Asian summer monsoon and persistent anomalies of extratropical circulation. The long persistence of block-ing over the Ural Mountains is a conspicuous feature. The physical processes responsible for the prolonged maintenance of this key system are investigated in terms of internal forcing (transient eddy upon basic flow) and external forcing (tropical heating forcing) via diagnosis and numerical experiments in the paper.
TL;DR: In this paper, two coupled global climate models, the Climate System Model (CSM) and the Parallel Climate Model (PCM), were used to simulate the 20th century climate using historical greenhouse gas and sulfate aerosol forcing, and simulated changes in temperature, precipitation, and soil moisture over the Asia-Pacific region (10°-60°N, 55°-155°E) with a focus on the East Asian summer monsoon rainfall and climate changes over the upper reaches of the Yangtze River.
Abstract: The Climate System Model (CSM) and the Parallel Climate Model (PCM), two coupled global climate models without flux adjustments recently developed at NCAR, were used to simulate the 20th century climate using historical greenhouse gas and sulfate aerosol forcing. These simulations were extended through the 21st century under two newly developed scenarios, a business-as-usual case (BAU, CO2 ≈ 710 ppmv in 2100) and a CO2 stabilization case (STA550, CO2 ≈ 540 ppmv in 2100). The simulated changes in temperature, precipitation, and soil moisture over the Asia-Pacific region (10°–60°N, 55°–155°E) are analyzed, with a focus on the East Asian summer monsoon rainfall and climate changes over the upper reaches of the Yangtze River. Under the BAU scenario, both the models produce surface warming of about 3–5°C in winter and 2–3°C in summer over most Asia. Under the STA550 scenario, the warming is reduced by 0.5–I.0°C in winter and by 0.5°C in summer. The warming is fairly uniform at the low latitudes and does not induce significant changes in the zonal mean Hadley circulation over the Asia-Pacific domain. While the regional precipitation changes from single CSM integrations are noisy, the PCM ensemble mean precipitation shows 10%–30% increases north of ~ 30°N and ~ 10% decreases south of ~ 30°N over the Asia-Pacific region in winter and 10%–20% increases in summer precipitation over most of the region. Soil moisture changes are small over most Asia. The CSM single simulation suggests a 30% increase in river runoff into the Three Gorges Dam, but the PCM ensemble simulations show small changes in the runoff.
TL;DR: In this article, a coupled atmosphere-ocean general circulation model is used to forecast the SST anomalies in the tropical Pacific at the background of the coupled model climatology, and a series of 24-month hindcasts for the period from November 1981 to December 1997 are carried out to validate the performance of coupled system.
Abstract: Predictions of ENSO are described by using a coupled atmosphere-ocean general circulation model. The initial conditions are created by forcing the coupled system using SST anomalies in the tropical Pacific at the background of the coupled model climatology. A series of 24-month hindcasts for the period from November 1981 to December 1997 are carried out to validate the performance of the coupled system. Corre-lations of SST anomalies in the Nino3 region exceed 0.54 up to 15 months in advance and the rms errors are less than 0.9°C. The system is more skillful in predicting SST anomalies in the 1980s and less in the 1990s. The model skills are also seasonal-dependent, which are lower for the predictions starting from late autumn to winter and higher for those from spring to autumn in a year-time forecast length. The prediction, begin-ning from March, persists 8 months long with the correlation skill exceeding 0.6, which is important in pre-dictions of summer rainfall in China. The predictions are succesful in many aspects for the 1997–2000 ENSO events.
TL;DR: The authors showed that the frequency of extreme heat-stress events in China, caused by extremely hot and humid days as well as by heatwaves lasting for a few days, has increased over the period from 1951 to 1994.
Abstract: In the past half century, the mean summertime temperature in China has increased, with nights warming more than days. Using surface station observations, we show that the frequency of extreme heat-stress events in China, caused by extremely hot and humid days as well as by heatwaves lasting for a few days, has increased over the period from 1951 to 1994. When humidity is high, hot weather can cause heat stress in humans. The increased heat-stress trend may pose a public health problem.
Abstract: The associations of onset and withdrawal of the rainy season in South Korea (called Changma) have been examined Composite studies showed that there are significant differences in circulations between extremely early and late onset (or withdrawals) not only over East Asia, but also over remote areas The in situ significant differences include the upper-level jet over East Asia and the subtropical anticyclone over the western North Pacific at lower levels The significant remote associations include the Indian monsoon and ENSO The Indian summer monsoon is related to both onset and withdrawal of the Changma, while ENSO has a significant relation only to onset, but not to withdrawal
TL;DR: Based on the method of estimating the diurnal amplitude of sea surface temperature (SST) as a function of daily averaged wind speed, precipitation and peak surface radiation, a parameterization scheme of diurnal cycle of SST is developed in this paper.
Abstract: Based on the method of estimating the diurnal amplitude of sea surface temperature (SST) as a function of daily averaged wind speed, precipitation and peak surface radiation, a parameterization scheme of diurnal cycle of SST is developed in the present study, Integrations to National Center for Atmospheric Research (NCAR) Community Climate Model (CCM3), separately forced by observed weekly SSTs with and without diurnal cycle of SST, are compared. Surface observation obtained from the Improved Meteorology (IMET) buoy during TOGA COARE Intensive Observation Period is applied to verify the SST parameterization, as well as a validation to the results from the CCM3 simulation. It is shown that the superposition of diurnal cycle of SST to the forced weekly SST makes a more realistic representation of the surface structure of intraseasonal oscillation over the western Pacific warm pool.