THE RELATIONSHIP BETWEEN THE ATMOSPHERIC HEATING SOURCE/SINK ANOMALIES OF ASIAN MONSOON AND FLOOD/DROUGHT IN THE YANGTZE RIVER BASIN IN THE MEIYU PERIOD

NCEP/NCAR reanalysis data and a 30-year precipitation dataset of observed daily rainfall from 109 gauge stations are utilized in this paper.Using the REOF we analyzed the spatial distribution of precipitation in the 109 stations in the Yangtze River Basin in Meiyu periods from 1978 to 2007.The result showed that the spatial distribution of precipitation in the Yangtze River Basin can be divided into the south and north part.As a result,relationships between an atmospheric heating source(hereafter called <Q_1>) over the Asian region and the precipitation on the south and north side of Yangtze River in Meiyu periods were separately studied in this paper.The results are shown as follows.The flood/drought to the north of Yangtze River(NYR) was mainly related to the <Q_1> over the East Asia summer monsoon region:when the <Q_1> over the Philippines through Western Pacific and the south China was weakened(strengthened),it would probably result in the flood(drought) in NYR;and the precipitation on the south side of Yangtze River(SYR)was related to the <Q_1> over the east Asia and Indian summer monsoon region:when the <Q_1> over the areas from south China to the northern East China Sea and Yellow Sea and south-eastern Japan was strengthened(weakened),and the <Q_1> over the areas from the Bay of Bengal to south-eastern Tibetan Plateau was weakened(strengthened),it will lead to flood(drought) in SYR.

CHARACTERISTICS OF THE SURFACE AND ATMOSPHERIC HEATING FIELDS OVER QINGHAI-XIZANG PLATEAU FOR THE PERIOD FROM AUGUST 1982 TO JULY 1983

The surface and atmospheric heating fields over the Qinghai-Xizang Plateau are computed by using the observational data of solar radiation during 1982—1983.The mian results are as follows:The central and northern parts of the Plateau act as heat sinks in winter from November to January.Both eastern and south- ern parts of the Plateau are of heat sources.In summer,the main part of the Plateau acts as a strong heat source,and the center of the heating field is in the southeastern Plateau.However the main part of the Plateau acts as a heat sink for the atmospheric heating fields from October to March.The maximum intensity of the atmospheric heat sink over the central Plateau appears in December and January.From April to September,the main part of the Plateau acts as a heat source for the atmospheric heating fields.

CHARACTERISTICS OF ATMOSPHERIC HEATING AND ATMOSPHERIC CIRCULATION DURING ACTIVE PERIOD OF 500 hPa HIGH OVER THE TIBETAN PLATEAU IN SUMMER

In correspondence with the establishment of the“upper high and lower high”pressure pattern due to the activities of 500 hPa high over the Tibetan Plateau in summer,a series of changes of the East Asia atmospheric circulation will take place.In this paper,the distributions of divergence and vertical velocity of 500 hPa high,the evolutions of atmos- pheric heat source,the variations of vorticity and zonal wind at 100 hPa level and vertical meridional cell over the Tibetan Plateau etc.are statistically analyzed.Thus,we can see that the ascending motion and the convective heating over the Tibetan Plateau,the South Asia high and the westerly jet on the north of the Plateau at 100 hPa level are weak- ened.The northern branch and the southern branch of the easterly jet on the south of the Plateau merge into a single whole and situate on the south of the former northern branch.In the meantime,thermodynamic land-sea discrepancy in South Asia and the convective heating over the Bay of Bengal is enhanced.It will play an important role in the mainte- nance of the easterly jet and the South Asia monsoon.

GLOBAL ATMOSPHERIC SEASONAL-MEAN HEATING:DIABATIC VERSUS TRANSIENT HEATING

With the ERA40 reanalysis daily data for 1958-2001, the global atmospheric seasonal-mean diabatic heating and transient heating are computed by using the residual diagnosis of the thermodynamic equation. The three-dimensional structures for the two types of heating are described and compared. It is demonstrated that the diabatic heating is basically characterized by strong and deep convective heating in the tropics, shallow heating in the midlatitudes and deep cooling in the subtropics and high-latitudes. The tropical diabatic heating always shifts towards the summer hemisphere, but the midlatitude heating and high-latitude cooling tend to be strong in the winter hemisphere. On the other hand, the transient heating due to transient eddy transfer is characterized by a meridional dipole pattern with cooling in the subtropics and heating in the mid- and high-latitudes, as well as by a vertical dipole pattern in the midlatitudes with cooling at lower levels and heating in the mid- and higher-levels, which gives rise to a sloped structure in the transient heating oriented from the lower levels in the high latitudes and higher levels in the midlatitudes. The transient heating is closely related to a storm track along which the transient eddy activity is much stronger in the winter hemisphere than in the summer hemisphere. In Northern Hemisphere, the transient heating locates in the western oceanic basin, while it is zonally-oriented in Southern Hemisphere, for which the transient heating and cooling are far separated over South Pacific during the cold season. The transient heating tends to cancel the diabatic heating over most of the globe. However, it dominates the mid-tropospheric heating in the midlatitudes. Therefore, the atmospheric transient processes act to help the atmosphere gain more heat in the high-latitudes and in the mid-troposphere of midlatitudes, reallocating the atmospheric heat obtained from the diabatic heating.

Time-lagged Effects of the Spring Atmospheric Heat Source over the Tibetan Plateau on Summer Precipitation in Northeast China during 1961–2020:Role of Soil Moisture

The spring atmospheric heat source(AHS)over the Tibetan Plateau(TP)has been suggested to affect the Asian summer monsoon and summer precipitation over South China.However,its influence on the summer precipitation in Northeast China(NEC)remains unknown.The connection between spring TP AHS and subsequent summer precipitation over NEC from 1961 to 2020 is analyzed in this study.Results illustrate that stronger spring TP AHS can enhance subsequent summer NEC precipitation,and higher soil moisture in the Yellow River Valley-North China region(YRVNC)acts as a bridge.During spring,the strong TP AHS could strengthen the transportation of water vapor to East China and lead to excessive rainfall in the YRVNC.Thus,soil moisture increases,which regulates local thermal conditions by decreasing local surface skin temperature and sensible heat.Owing to the memory of soil moisture,the lower spring sensible heat over the YRVNC can last until mid-summer,decrease the land–sea thermal contrast,and weaken the southerly winds over the East Asia–western Pacific region and convective activities over the South China Sea and tropical western Pacific.This modulates the East Asia–Pacific teleconnection pattern,which leads to a cyclonic anomaly and excessive summer precipitation over NEC.

Atmospheric Diabatic Heating and Summertime Circulation in Asia-Africa Area

Utilizing data from NCEP/ NCAR reanalysis, the summertime atmospheric diabatic heating due to different physical processes is investigated over the Sahara desert, the Tibetan Plateau, and the Bay of Bengal. Atmospheric circulation systems in summer over these three areas are also studied. Thermal adaptation theory is employed to explain the relationship between the circulation and the atmospheric diabatic heating. Over the Sahara desert, heating resulting from the surface sensible heat flux dominates the near-surface layer, while radiative cooling is dominant upward from the boundary layer. There is positive vorticity in the shallow boundary layer and negative vorticity in the middle and upper troposphere. Downward motion prevails over the Sahara desert, except in the shallow near—surface layer where weak ascent exists in summer. Over the Tibetan Plateau, strong vertical diffusion resulting from intense surface sensible heat flux to the overlying atmosphere contributes most to the boundary layer heating, condensation associated with large—scale ascent is another contributor to the lower layer heating. Latent heat release accompanying deep convection is critical in offsetting longwave radiative cooling in the middle and upper troposphere. The overall diabatic heating is positive in the whole troposphere in summer, with the most intense heating located in the boundary layer. Convergence and positive vorticity occur in the shallow near—surface layer and divergence and negative vorticity exist deeply in the middle and upper troposphere. Accordingly, upward motion prevails over the Plateau in summer, with the most intense rising occurring near the ground surface. Over the Bay of Bengal, summertime latent heat release associated with deep convection exceeds longwave radiative cooling, resulting in intense heating in almost the whole troposphere. The strongest heating over the Bay of Bengal is located around 400 hPa, resulting in the most intense rising occurring between 300 hPa and 400 hPa, and producing positive vorticity in the lower troposphere and negative vorticity in the upper troposphere. It is also shown that the divergent circulation is from a heat source region to a sink region in the upper troposphere and vice versa in lower layers. Key words Atmospheric diabatic heating - Summer - Circulation This work was jointly supported by “ National Key Program for Developing Basic Sciences” G1998040904 by NSFC projects 49805003, 49635170, 49823002, and 49825504.

Numerical Modelling of the Effects of Ozone on the Summer Atmospheric Circulation

The effects of ozone on the summer atmospheric general circulation are simulated by use of a zonal model with the pesigma coordinate system. Results show that the simulated properties at the upper levels are remarkably improved after the ozone effects are introduced to the model. The direct effect of ozone is to enhance the heating rates at the upper levels. In the lower atmosphere. this effect is very little. Furthermore, the ozone can change the distributions and values of other components of heating fields, resulting in the change of the total heating rates, and meanwhile induce evident variation of atmospheric circulation at the lower levels.

Uncertainties in Quantitatively Estimating the Atmospheric Heat Source over the Tibetan Plateau

As a huge,intense,and elevated atmospheric heat source(AHS) approaching the mid-troposphere in spring and summer,the Tibetan Plateau(TP) thermal forcing is perceived as an important factor contributing to the formation and variation of the Asian summer monsoon.Despite numerous studies devoted to determine the strength and change of the thermal forcing of the TP on the basis of various data sources and methods,uncertainties remain in quantitative estimation of the AHS and will persist for the following reasons:(1) Routine meteorological stations cover only limited regions and show remarkable spatial inhomogeneity with most distributed in the central and eastern plateau.Moreover,all of these stations are situated at an altitude below 5000 m.Thus,the large area above that elevation is not included in the data.(2) Direct observations on heat fluxes do not exist at most stations,and the sensible heat flux(SHF) is calculated by the bulk formula,in which the drag coefficient for heat is often treated as an empirical constant without considering atmospheric stability and thermal roughness length.(3) Radiation flux derived by satellite remote sensing shows a large discrepancy in the algorithm in data inversion and complex terrain.(4) In reanalysis data,besides the rare observational records employed for data assimilation,model bias in physical processes induces visible errors in producing the diabatic heating fields.

Structural Variation of an Atmospheric Heat Source over the Qinghai-Xizang Plateau and Its Influence on Precipitation in Northwest China

NCEP/NCAR reanalysis data and a 47-year precipitation dataset are utilized to analyze the relationship between an atmospheric heat source （hereafter called 〈 Q1 〉） over the Qinghai-Xizang Plateau （QXP） and its surrounding area and precipitation in northwest China. Our main conclusions are as follows： （1） The horizontal distribution of 〈 Q1 〉 and its changing trend are dramatic over QXP in the summer. There are three strong centers of 〈 Q1 〉 over the south side of QXP with obvious differences in the amount of yearly precipitation and the number of heat sinks predominate in the arid and semi-arid regions of northwest China （NWC）, beside the northern QXP with an obvious higher intensity in years with less precipitation. （2） In the summer, the variation of the heat source＇s vertical structure is obviously different between greater and lesser precipitation years in eastern northwest China （ENWC）. The narrow heat sink belt forms between the northeast QXP and the southwestern part of Lake Baikal. In July and August of greater precipitation years, the heating center of the eastern QXP stays nearly over 35°N, and at 400 hPa of the eastern QXP, the strong upward motion of the heating center constructs a closed secondary vertical circulation cell over the northeast QXP （40~ 46~N）, which is propitious to add precipitation over the ENWC. Otherwise, the heating center shifts to the south of 30°N and disappears in July and August of lesser precipitation years, an opposite secondary circulation cell forms over the northeast QXP, which is a disadvantage for precipitation. Meanwhile, the secondary circulation cell in years with more or less precipitation over the ENWC is also related to the heat source over the Lake Baikal. （3） The vertical structure of the heat source over the western QXP has obvious differences between greater and lesser precipitation years in western northwest China in June and July. The strong/weak heat source over the western QXP produces relatively strong/weak ascending motion and correspondingly constructs a secondary circulation cell in lesser/greater precipitation years.

Varying Rossby Wave Trains from the Developing to Decaying Period of the Upper Atmospheric Heat Source over the Tibetan Plateau in Boreal Summer

This study demonstrates the two different Rossby wave train（RWT） patterns related to the developing/decaying upper atmospheric heat source over the Tibetan Plateau（TPUHS） in boreal summer. The results show that the summer TPUHS is dominated by quasi-biweekly variability, particularly from late July to mid-August when the subtropical jet steadily stays to the north of the TP. During the developing period of TPUHS events, the intensifying TPUHS corresponds to an anomalous upper-tropospheric high over the TP, which acts as the main source of a RWT that extends northeastward, via North China, the central Pacific and Alaska, to the northeastern Pacific region. This RWT breaks up while the anomalous high is temporarily replaced by an anomalous low due to the further deepened convective heating around the TPUHS peak. However, this anomalous low, though existing for only three to four days due to the counteracting dynamical effects of the persisting upper/lower divergence/convergence over the TP, acts as a new wave source to connect to an anomalous dynamical high over the Baikal region. Whilst the anomalous low is diminishing rapidly, this Baikal high becomes the main source of a new RWT, which develops eastward over the North Pacific region till around eight days after the TPUHS peak. Nevertheless, the anomaly centers along this decaying-TPUHS-related RWT mostly appear much weaker than those along the previous RWT.Therefore, their impacts on circulation and weather differ considerably from the developing to the decaying period of TPUHS events.

Formation and Variation of the Atmospheric Heat Source over the Tibetan Plateau and Its Climate Effects

To cherish the memory of the late Professor Duzheng YE on what would have been his 100 th birthday, and to celebrate his great accomplishment in opening a new era of Tibetan Plateau（TP） meteorology, this review paper provides an assessment of the atmospheric heat source（AHS） over the TP from different data resources, including observations from local meteorological stations, satellite remote sensing data, and various reanalysis datasets. The uncertainty and applicability of these heat source data are evaluated. Analysis regarding the formation of the AHS over the TP demonstrates that it is not only the cause of the atmospheric circulation, but is also a result of that circulation. Based on numerical experiments, the review further demonstrates that land–sea thermal contrast is only one part of the monsoon story. The thermal forcing of the Tibetan–Iranian Plateau plays a significant role in generating the Asian summer monsoon（ASM）, i.e., in addition to pumping water vapor from sea to land and from the lower to the upper troposphere, it also generates a subtropical monsoon–type meridional circulation subject to the angular momentum conservation, providing an ascending-air large-scale background for the development of the ASM.

A STUDY ON THE CHARACTERISTICS AND EFFECT OF THE LOW-FREQUENCY OSCILLATION OF THE ATMOSPHERIC HEAT SOURCE OVER THE EASTERN TIBETAN PLATEAU

There has been a lot of discussion about the atmospheric heat source over the Tibetan Plateau(TP)and the low-frequency oscillation of atmospheric circulation.However,the research on low-frequency oscillation of heat source over TP and its impact on atmospheric circulation are not fully carried out.By using the vertically integrated apparent heat source which is calculated by the derivation method,main oscillation periods and propagation features of the summer apparent heat source over the eastern TP(Q1ETP)are diagnosed and analyzed from 1981 to 2000.The results are as follows:(1)Summer Q1ETP has two significant oscillation periods:one is 10-20d(BWO,Quasi-Biweekly Oscillation)and the other is 30-60d(LFO,Low-frequency Oscillation).(2)A significant correlation is found between Q1ETP and rainfall over the eastern TP in 1985 and 1992,showing that the low-frequency oscillation of heat source is likely to be stimulated by oscillation of latent heat.(3)The oscillation of heat source on the plateau mainly generates locally but sometimes originates from elsewhere.The BWO of Q1ETP mainly exhibits stationary wave,sometimes moves out(mainly eastward),and has a close relationship with the BWO from the Bay of Bengal.Showing the same characteristics as BWO,the LFO mainly shows local oscillation,occasionally propagates(mainly westward),and connects with the LFO from East China.In summary,more attention should be paid to the study on BWO of Q1ETP.

RELATIONSHIP BETWEEN THE 30 TO 60 DAY OSCILLATION OF ATMOSPHERIC HEAT SOURCE AND THE DROUGHT AND FLOOD EVENTS IN JUNE IN THE SOUTH OF CHINA

Based on the NCEP/NCAR reanalysis data and the observed precipitation data in the south of China from 1958 to 2000,the impact of 30 to 60 day oscillation of atmospheric heat sources on the drought and flood events in June in the south of China is discussed.During the flood(drought) events,there exists an anomalous low-frequency anticyclone(cyclone) at the low level of the troposphere over the South China Sea and the northwestern Pacific,accompanied with anomalous low-frequency heat sinks(heat sources),while there exists an anomalous low-frequency cyclone(anticyclone) with anomalous heat sources(sinks) over the area from the south of China to the south of Japan.On average,the phase evolution of the low-frequency in drought events is 7 to 11 days ahead of that in flood events in May to June in the south of China.In flood events,low-frequency heat sources and cyclones are propagated northward from the southern South China Sea,northwestward from the warm pool of the western Pacific and westward from the northwestern Pacific around 140°E,which have very important impact on the abundant rainfall in June in the south of China.However,in drought events,the northward propagations of the low-frequency heat sources and cyclones from the South China Sea and its vicinity are rather late compared with those in flood events,and there is no obvious westward propagation of the heat sources from the northwestern Pacific.The timing of the low-frequency heat source propagation has remarkable impact on the June rainfall in the south of China.

Characteristics of Atmospheric Heat Sources in the Tibetan Plateau-Tropical Indian Ocean Region

Investigating the temporal and spatial distributions of the atmospheric heat sources(AHS)over the Tibetan Plateau-Tropical Indian Ocean(TP-TIO)region is of great importance for the understanding of the evolution and development of the South Asian summer monsoon(SASM).This study used the Japanese 55-year Reanalysis(JRA-55)data from 1979 to 2016 and adopted statistical methods to study the characteristics of the AHS between the TP and TIO,and theirs link to the SASM on an interannual scale.The results indicated that the monthly variations of the AHS in the two regions were basically anti-phase,and that the summer AHS in the TP was obviously stronger than that in the TIO.There were strong AHS and atmospheric moisture sink(AMS)centers in both the eastern and western TP in summer.The AHS center in the east was stronger than that in the west,and the AMS centers showed the opposite pattern.In the TIO,a strong AHS center in the northwest-southeast direction was located near 10°S,90°E.Trend analysis showed that summer AHS in the TIO was increasing significantly,especially before 1998,whereas there was a weakening trend in the TP.The difference of the summer AHS between the TP and TIO(hereafter IQ)was used to measure the thermal contrast between the TP and the TIO.The IQ showed an obvious decreasing trend.After 1998,there was a weak thermal contrast between the TP and the TIO,which mainly resulted from the enhanced AHS in the TIO.The land-sea thermal contrast,the TIO Hadley circulation in the southern hemisphere and the SASM circulation all weakened,resulting in abnormal circulation and abnormal precipitation in the Bay of Bengal(BOB).

The impact of concurrent variation of atmospheric meridional heat transport in western Baffen Bay and eastern Greenland on summer Arctic sea ice

Based on the climatological reanalysis data of the European Center for Medium-Range Weather Forecasts and the Arctic sea ice data of the National Snow and Ice Data Center, the relationship between the Arctic sea ice area(SIA)and the interannual variation of atmospheric meridional heat transport(AMHT) was analyzed. The results show that the atmospheric meridional heat transported by transient eddy(TAMHT) dominates the June AMHT in midhigh latitudes of the Northern Hemisphere, while the western Baffin Bay(B) and the eastern Greenland(G) are two gates for TAMHT entering the Arctic. TAMHT in the western Baffin Bay(B-TAMHT) and eastern Greenland(G-TAMHT) has a concurrent variation of reverse phase, which is closely related to the summer Arctic SIA.Possible mechanism is that the three Arctic atmospheric circulation patterns(AD, AO and NAO) in June can cause the concurrent variation of TAMHT in the B and G regions. This concurrent variation helps to maintain AD anomaly in summer through wave action and changes the polar air temperature, thus affecting the summer Arctic SIA. Calling the heat entering the Arctic as warm transport and the heat leaving Arctic as cold transport, then the results are classified into three situations based on B-TAMHT and G-TAMHT: warm B corresponding to cold G(WC), cold B corresponding to warm G(CW), cold B corresponding to cold G(CC), while warm B corresponding to warm G is virtually non-existent. During the WC situation, the SIA in the Pacific Arctic sediments and Kara Sea decreases;during the CW situation, the SIA in the Laptev Sea and Kara Sea decreases;during the CC situation, the SIA in the Kara Sea, Laptev Sea and southern Beaufort Sea increases.

Interdecadal Variations of the March Atmospheric Heat Source over the Southeast Asian Low-Latitude Highlands

Based on the fifth-generation reanalysis dataset from the European Centre for Medium-Range Weather Forecasts for 1979–2019,we investigated the effects of the circumglobal teleconnection(CGT)on the interdecadal variation of the March atmospheric heat source(AHS)over the Southeast Asian low-latitude highlands(SEALLH).The dominant mode of the March AHS over the SEALLH features a monopole structure with an 8–11-year period.Decadal variations in the AHS make an important contribution to the 11-year low-pass filtered component of the AHS index,whichexplains 54.3%of the total variance.The CGT shows a clear interdecadal variation,which explains 59.3%of the total variance.The March AHS over the SEALLH is significantly related to the CGT on interdecadal timescales.When the CGT is optimally excited by a significant cyclonic vorticity source near northern Africa(i.e.,in its positive phase),the SEALLH is dominated by anomalous southerly winds and ascending motions on the east of the anomalous cyclone.The enhanced advection and upward transfer result in a high-enthalpy air mass that converges into and condenses over the SEALLH,leading to a largerthan-average March AHS over this region.The key physical processes revealed by this diagnostic analysis are supported by numerical experiments.

Impacts of the atmospheric apparent heat source over the Tibetan Plateau on summertime ozone vertical distributions over Lhasa

The Tibetan Plateau(TP)is an area sensitive to climate change,where the ozone distribution affects the atmospheric environment of the TP and its surrounding regions.The relatively low total column ozone over the TP in boreal summer and its spatiotemporal variations have received extensive attention.In this study,five-year balloon-borne measurements of ozone over Lhasa in boreal summer are used to investigate the influences of the apparent heat source(Q1)on the ozone vertical structure over the plateau.The mechanisms for the above processes are also explored.The results show that the tropospheric ozone mixing ratio over Lhasa decreases when the total atmospheric Q1 in the troposphere over the TP is relatively high.Strengthened ascending motions are accompanied by enhanced Q1 over the main TP region.Consequently,the tropospheric ozone mixing ratio over Lhasa decreases when Q1 is higher in summer,which is attributed to the upward transport of the ozone-poor surface air.

INTERANNUAL VARIATIONS OF ATMOSPHERIC HEAT SOURCES AND MOISTURE SINKS OVER THE EQUATORIAL PACIFIC AND THEIR RELATIONS TO THE SST ANOMALIES

The interannual variations of atmospheric heat sources and moisture sinks over the Equatorial Pacific and their relations with the SST anomalies are studied using ECMWF reanalysis data from 1979 to 1993. It is found by singular value decomposition (SVD) analysis that the region in the tropical Pacific with high positive correlation between the vertically integrated heat source <Q1> anomaly and the SST anomaly, and between the vertically integrated moisture sink <Q2> anomaly and the SST anomaly, is mainly located in a long and narrow belt to the east of 170 °E between 5 °S and 5 °N. The analysis of the vertical structure of atmospheric heat sources and moisture sinks shows that the interannual variations of Q1, Q2 and SST in the equatorial central and eastern Pacific are strongly and positively correlated in the whole troposphere except the bottom (962.5 hPa) and the top (85 hPa) layers. However, in the western Pacific, the interannual variations of Q1 below 850 hPa is negatively related to the SST. The correlation coefficient at the level 962.5 hPa reaches even –0.59. In other layers the positive correlation between the interannual variations of Q1, Q2 and the SST are weak in the western Pacific.

CHARACTERISTICS OF ATMOSPHERIC HEAT SOURCE ASSOCIATED WITH THE SUMMER MONSOON ONSET OVER THE SOUTH CHINA SEA AND THE POSSIBLE MECHANISM RESPONSIBLE FOR ITS LATE OR EARLY ONSET

The characteristics of atmospheric heat source associated with the summer monsoon onset in the South China Sea (SCS) are studied using ECMWF reanalysis data from 1979 to 1993. A criterion of the SCS summer monsoon onset is defined by the atmospheric heat source. Applying this criterion to the 15-year (1979 – 1993) mean field, the onset of the SCS summer monsoon is found to occur in the fourth pentad of May. And this criterion can also give reasonable results for the onset time of the SCS summer monsoon on a year-to-year basis. In addition, pretty high correlation has been found between the onset time of the SCS summer monsoon and the zonal mean vertically integrated heat source <Q1> at 40°S in April. The causes for the late or early onset of the SCS summer monsoon and the close relationship between the onset time and the zonal mean vertically integrated heat source <Q1> at 40 °S in April might be explained by the variations in intensity of the Hadley circulation.

The Rossby wave train patterns forced by shallower and deeper Tibetan Plateau atmospheric heat-source in summer in a linear baroclinic model

By using a linear baroclinic model(LBM),this study investigates the different Rossby wave train(RWT)patterns associated with the Tibetan Plateau(TP)upper-atmospheric heat source(TPUHS)that is anomalously shallower and deeper in boreal summer.Observational results indicate the different RWT patterns between the developing and decaying periods of synoptic TPUHS events,when the anomalous TPUHS develops from a relatively shallower to a deeper TP heat source.Based on the different vertical heating profiles between these two periods in observation,this study forces the LBM with prescribed TPUHS profiles to mimic a shallower and deeper summer TP heat source.The results show that the atmospheric responses to a shallower and deeper TPUHS do exhibit different RWT patterns that largely resemble those in observation.Namely,corresponding RWT pattern to a shallower TPUHS stretches from the TP to the west coast of America,while that to a deeper TPUHS extends from the TP region to Alaska.