| The intense diabatic heating over the Tibetan Plateau affects the movement of the atmosphere over and around the Tibetan Plateau,which will have an important impact on the occurrence and development of weather and climate in China and even in East Asia.However,due to the influence of topography,model resolution and calculation method,the spatial and temporal distribution of the diabatic heating anomalies and the estimation of each heating component over the Tibetan Plateau have great uncertainties.In this paper,the applicability of diabatic heating of ERA5,NCEPII,JRA55 and MERRA2 reanalysis data over the Tibetan Plateau is evaluated against observations.The spatial and temporal differences of the diabatic heating over the Tibetan Plateau are compared using two methods:forward algorithm and reverse algorithm.On these basis,the relationship between the spring sensible heat anomaly over the Tibetan Plateau and summer precipitation over eastern China is analyzed.The main conclusions of this paper are as follows:(1)There are significant temporal and spatial differences in surface sensible heat flux and latent heat flux over the Tibetan Plateau from observation and reanalysis.The reanalysis data of ERA5 were closest to the observations,and the difference between NCEPII and the observations was the largest.The peak value of sensible heat appeared in spring,and the difference between observation and reanalysis data was up to 60 W/m~2.The maximum latent heat occurred in summer,and the difference between observed and reanalyzed data was up to 20 W/m~2.The four reanalysis data reproduce better latent heat flux than sensible heat flux.The applicability analysis of the sensible latent heat of the reanalysis data in the northwest,northeast,southwest and southeast regions of the Tibetan Plateau show that the reanalysis data in the northeast part of the Plateau are in the best agreement with the observations.The average deviation is 5?50 W/m~2 on the southern slope of the Plateau.For the southeastern part of the Plateau,the sensible latent heat simulated by different reanalysis data has the most significant difference in January-May and October-December,with a maximum of 150 W/m~2.The comparison between ERA5 reanalysis data and observations on typical sunny days show that there are significant diurnal variation characteristics of ERA5 and the observed sensible heat,latent heat,net radiation,net short-wave radiation and net long wave radiation,and the maximum value of ERA5 appears at 12:00?15:00(Beijing standard time).Under sunny conditions in summer,the difference between ERA5 and the observed sensible heat and net radiation is the largest in the southeastern part of the Plateau,which is between 100and 300 W/m~2.Under sunny conditions in spring and autumn,the deviation between ERA5 and the observed sensible heat and net radiation in the northeast,southeast and northwest of the Plateau is small,which is less than 30 W/m~2.Under sunny conditions in winter,the difference of net radiation and net long wave radiation between ERA5and observed is the greatest,especially in the northwestern Plateau(up to 200 W/m~2).(2)On the interannual scale,the surface sensible heat flux and latent heat flux over the Tibetan Plateau decreased and increased from 1979 to 2018,with the values of-0.08 W/m~2/10a and 0.53 W/m~2/10a,respectively.The net shortwave radiation increased at 0.12 W/m~2/10a and net long wave radiation decreased-0.30 W/m~2/10a.At the seasonal scale,the latent heat over the Tibetan Plateau increased in the year,which were0.46 W/m~2/10a,0.67 W/m~2/10a,0.82 W/m~2/10a and 0.17 W/m~2/10a,respectively.The sensible heat over the Tibetan Plateau had different changing trends in different seasons,and the main trend was as follows:the summer and autumn sensible heat show a decreasing trend of-0.24 W/m~2/10a;In spring,the sensible heat increased to 0.29W/m~2/10 a.In winter,the sensible heat over the Plateau decreased in the northern part of the Plateau and increased in the southern part of the Plateau.The net long wave radiation over the Plateau show a decreasing trend,which may be related to the increasing trend of surface albedo.In spring,summer and autumn,the net long wave radiation show a decreasing trend in the northwest and southwest of the Plateau,and the trend increased with the season.However,the net long wave radiation over the Plateau in winter shows a slight increasing trend.It is worth noting that the net shortwave radiation in the southwest of the Plateau has a significant downward trend in summer,and show a slight upward trend in the southeast of the Plateau.The maximum sensible heat in summer is in the north of Tanggula Mountain,the maximum sensible heat flux in spring is in the south of Tanggula Mountain,and the maximum latent heat in summer is in the whole Tibetan Plateau,which could be attributed to more precipitation and higher soil moisture.(3)The diabatic heating calculated by the positive algorithm indicates that the Plateau is basically the heat source,while the inversion algorithm indicates that the central part of the Plateau is the heat source and the marginal area of the Plateau is the cold source.In spring,the atmospheric heat source E obtained by the positive algorithm mainly appears in the southwest and eastern boundary of the Tibetan Plateau.In summer,the atmospheric heat source over most parts of the Plateau is more than 60 W/m~2,and it can reach 100 W/m~2 in the southern part of the Plateau.In winter,the heat source is the minimum,which is basically below 40 W/m~2.In the transition season of spring and autumn,latent heat and short-wave net radiation are more obvious,while the long wave net radiation has marginal variations.The spatial distribution characteristics of positive atmospheric heat source E and inverted heat source<Q1>are similar in the southern part of the Tibetan Plateau,and the strongest heat source E and<Q1>are found in the south of Tanggula Mountain in spring.The strongest heat sources of E and<Q1>are located in the southern part of the Tibetan Plateau in summer.In autumn,E and<Q1>were cold sources in the western part of the Plateau,and heat sources in the southeastern margin of the Plateau.In winter,E and<Q1>are generally cold sources over the Tibetan Plateau,but there is still a small part of heat sources on the southern slope of the Plateau,which may be related to the steep topography of the southern slope,abundant water vapor,and the release of latent heat of precipitation on the windward slope,the heat source intensity in the southern slope of the Tibetan Plateau is most prominent and ranges from 50 to 400 W/m~2.(4)From 1979 to 2018,the first main mode of EOF of the spring sensible heat over the Tibetan Plateau show that the interannual variation characteristics of the Tibetan Plateau show a uniform distribution,indicating that the spring sensible heat flux was on a seasonal scale.The change in the space is basically the same,and only in the northern part there are fewer inverted changes,that is,the change in sensible heat in the northern part show a weakening change compared with the Tibetan Plateau.The second main mode changes in the opposite direction in the north and south of the Tibetan Plateau,and its time coefficient also has a strong interannual variation.(5)The analysis of the relationship between the spring sensible heat over the Tibetan Plateau and the summer precipitation in eastern China show that:in the years when the sensible heat is strong,the South Asian high is eastward and its intensity increases,the western Pacific subtropical high weakens,the specific humidity of eastern China decreases,and summer precipitation Less.In the years when the sensible heat over the Tibetan Plateau is weak,the center of the South Asian High is southwest,the summer monsoon is slightly stronger,and the specific humidity of most parts of China and adjacent oceans increases,and eastern China has more summer precipitation. |
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