Using Doppler radar products from three intense convective precipitation events occurring on
the night of June 12, early morning and night on July 12, 2006 over the Tianjin area, a comparative study
is made, showing that typically, the radial velocity field changes earlier than does the echo-intensity field
at the initial and mature stages of precipitation, such that much attention should be paid to the variation in
the velocity field in doing nowcasts of rainfall, and the Doppler velocity variation in conjunction with
Auto-Nowcaster predictions helps determine the change in radar echo intensity and its movement
direction, thereby improving the accuracy of nowcasts of strongly convective precipitation.
The Tibetan long-term monthly mean rainfall exhibits a SE to NW decrease, showing strong regionality. The summertime vigorous rainfall centers are roughly coincident with those of heat sources <Q1> averaged throughout the atmospheric extent, with latent heating making the greatest contribution to <Q1>. In the heat source stronger (weaker) year than normal, the western Pacific subtropical high amplifies (falls off), making westward extension (eastward withdrawal); the South-Asian high intensifies (weakening), eastward expanding (westward extending); summer monsoon becomes intense (enfeebled). In that case, the precipitation is more (less) in the Jiang-Huai valley compared to normal in relation to the rainfall lower (higher) than mean over the littoral provinces of South China, and two parallel anomalously deep wavetrains (just one wavetrain) of cyclones alternate with anti-cyclones over the Pacific.
In the context of 1960~2003 summertime rainfall and small-sized pan evaporations from 131 stations distributed over NW China covering Xinjiang, Qinghai, Gansu, Ningxia, Shaanxi as well as western Nei Mongolia, and Arctic Oscillation Indices (AOI) we define a homogenized index for aridity or wetness feature, with which to examine the relations between AOI and NW China aridity-wetness regime, indicating their noticeable relations on an interdecadal basis. It is found that during the decade of summer Arctic oscillation stronger than mean, the sea level pressure field shows positive (negative) anomalies over Asian landmass, a stronger anticyclonic anomaly circulation appears at 700 hPa over Lake Baikal and to the south, westerly (northerly) departure emerges in the westerly (monsoon) portion of NW China, as well as over NW China there appears a structure with a low in the west and a high in the east at the 500 hPa height field, suggestive of east-Asian summer monsoon weaker than normal such that westerly flows prevail in the westerly zone of NW China, leading to rainfall more than mean for a wetter climate while in its monsoon area the northerly winds are dominant, with precipitation less than normal, resulting in a climate drier in comparison to mean and v.v. for the decade with summer AO weaker than normal.
Analysis based on remote sensing data and NCEP/NCAR reanalysis datasets finds that, on the basis of
composing the most typical 'South-Born-South-Persisting' WPSH double ridges processes, anomaly 500 hPa
stream field shows that the northern ridge vanishment is climatology, while there is a anomaly anticyclone in
the south ridge, making its development and persistence and leading to the WPSH locate much southward
than usual after the double ridges process ends. Further studies by the use of vorticity equation indicate that
150 hPa a anomaly anticyclone to the east of the WPSH south ridge region move westward, strengthening the
minus vorticty advection of the south ridge region and changing the vertical motion over WPSH region. It not
only changes the meridional wind distribution, leading to geostrophic vorticity advection intensify and the
anomaly anticyclone develop, but also brings the diabatic heating distribute vertically asymmetrically,
inducing a anomaly cyclone between the two ridges and a anomaly anticyclone above the south ridge.
Conclusively, the general circulation on the upper level plays an important role in the double ridges process
persistence.
ECMWF daily reanalysis is applied to investigate 1961-2001 heat source/sink and the climate features in relation to the
atmospheric heat distribution over the QTP (Qinghai-Tibetan Plateau) by means of the "inverse algorithm". Results
suggest that 1) in March - September (October - February), the QTP acts as a heat (cold) source, the strongest being in
June (December). For the region as a whole, the heat source feature lasts longer, with its intensity much higher compared
to the cold source; 2) as shown in the heating vertical profile, the maximum heat source layer occurs dominantly between
500-600 hPa, but with the season-dependent heating strength and depth, and, in contrast, the cold source has its
maximum layer and intensity varying as a function of time; 3) the horizontal distribution of the heat sources throughout
the troposphere 1> (from surface to 100 hPa) is complicated, displaying noticeable regionality, i.e., the heat source
changes faster in the western than in the eastern QTP, with the western source considerably stronger in April - August,
and intensified quickly enough to show a 200 W/m2 center in May, one month ahead of the eastern source. When July
comes the regional heat source begins to weaken towards the south, during which the western source weakens faster,
changing to a cold source in October, again one month earlier compared to the eastern counterpart; 4) since 1979 the
seasonal variability of the heat source has shown climate transition signals, as clearly seen in 1990/91.
KEYWORDS: Meteorology, Climatology, Lithium, Troposphere, Atmospheric sciences, Temperature metrology, System on a chip, Information science, Information technology, Floods
Based on analysis of the temperature latitudinal deviation on middle troposphere on a climate basis, its
seasonal cycle suggests that due to the Tibetan Plateau heating in spring, seasonal transition of the thermal
difference between East Asia continent and West Pacific first takes place on the subtropical region,
accompanied by the prevailing wind turning from northerly in winter to southerly in summer on low
troposphere The precipitation takes place at the same time. This maybe indicates the East Asian subtropical
summer monsoon onset. Consequently, it is advanced that the seasonal cycle formed by the zonal thermal
contrast between Asian continent and western Pacific may be an independent driving force of East Asian
subtropical monsoon.
Utilizing the NECP/NCAR reanalysis data, the annual atmospheric circulation over East Asia from 1981 to 2000 is
investigated. It is discovered that a zonal positive vorticity belt maintains to the south of Tibetan Plateau, due to the
interaction of the plateau boundary layer and its neighboring free atmosphere. Particularly, there is an obvious
topographic trough related to the positive vorticity near 90°E. According to this phenomenon, a Tibetan Plateau
Topographic Trough Index (TPTTI) is defined in the paper over the key areas (80-90°E, 25°N). The index is proved to be
effective in distinguishing between the characteristic of the Tibetan Plateau topographic trough (TPTT) and that of the
Bay of Bengal Trough (BOBT). The annual variation of the TPTT is closely related to the plateau heating source, and the
former's significant abrupt changes during April and June might be primarily induced by the seasonal sudden jump of the
latter. In winter, the low-level anticyclone caused by the Tibetan plateau cooling is strengthened and superimposes the
westerly wind that should have been strengthened by dynamic effect, which weakens the TPTT. However, in summer, the
low-level cyclone resulting from the Tibetan plateau heating strengthens the circumferential westerly and deepens the
TPTT. Further investigations indicate that there is a considerable relationship between the South China Sea summer
monsoon onset and the evolution of the TPTT and the BOBT. The TPTT propagates southward and the vortex near Sir
Lanka moves northward continuously, till they meet and interact over the Bay of Bengal. This is the direct process of the
subtropical high belt splitting initially over Bay of Bengal and the establishment of the BOBT. Subsequently, the
southwesterly wind becomes stronger and promotes the eastward retreat of subtropical high, causing the South China Sea
summer monsoon bursts over the whole South China Sea.
Under specific external environment and surrounding circulations, a northern and a southern line are
available at the same longitude in subtropical region on a synchronous basis, though the subtropical high has
characteristic of single ridge in most areas at most of time. We define this phenomenon as 'the double ridges
process'. It plays important roles on West Pacific Subtropical High (WPSH) discontinuous northward
advancement and southward retreat, further on the second Meiyu period of Changjiang River basin.
Furthermore, the moisture transport passage is changed when the process persists. The moisture is transported
northward and converged to the north of the ridges, leading to two rainbelt formed.
Subtropical high experiences double ridges process (DRP) nearly every year, of which the phase-locking
and geographical preference result in DRP occurrence in the WPSH on a climatological basis. In this study,
satellite data and the 43-yr mean climatology of NCEP/NCAR Reanalysis datasets are employed to examine
the characteristics of WPSH DRP during the period of May to October. Six cases are found to occur during
the period of late July to late September, indicating the preference time of the occurrences of WPSH DRP.
Unexceptionally, each of them is characterized by a new-born ridge in the south of WPSH which persists several days before its vanishment and by the maintanence of the original one in the northern portion of WPSH.
Based on 1982-1999 satellite sensings, meteorological data and observations of crop growth/development, a study is conducted on seasonal and interannual variations in vegetation NDVI (normalized difference vegetation index), its response to climate change and its relationship with crop growth/development during the period in Zhengzhou region of Henan province. Evidence suggests that the interannual change is not so pronounced in the regional NDVI, exhibiting, on the whole, an unsteadily increasing trend; stronger seasonality is shown in the annual variation, with a more significant rising trend in spring as opposed to those for summer and autumn; NDVI change is in positive correlation both to temperature and precipitation (stronger response to temperature), with its change subject dominantly to temperature and rainfall in spring and summer, respectively, under varying effect of temperature and precipitation in autumn, and largely under the impacts of heat in winter and during the growth of winter wheat and summer-sown corn the NDVI is positively correlated to the crop height and density (the number of crop individuals per unit area) in their milking stage, the latter acting as a principal factor of NDVI change.
Based on the TRMM (Tropical Rainfall Measuring Missio) remote sensing data, the relationship between the daily
precipitation and the SST (Sea Surface Temperature) in the low latitude ocean area were analyzed during the Asia
monsoon season in this paper. By calculated the corresponding and lag correlation coefficient of the precipitation and the
SST in the low latitude ocean area in different domain, the paper discussed the relationship between the daily
precipitation and the SST in these areas during the onset, the middle and the terminative period of Asia monsoon season.
The results shown that the relationship was differently in dissimilitude ocean area and period.
Through analyzing the mesoscale disturbance field of a Meiyu rainstorm, it is found that there are close relations between the development and propagation of inertia-gravitational waves, rain belts and low vortex. The propagating patterns of inertia-gravitational waves are different in the upper and lower levels. In the early period of precipitation, convective instability triggers the inertia-gravitational waves. When there are inertia-gravitational waves propagating southward in the upper and lower levels, it is favorable to form multi-rain belts. In the mid of precipitation, the inertia-gravitational waves in the upper-layer rotate anticlockwise with the lower-layer vortex center, and precipitation strengthens and moves eastward in the meantime. The inertia-gravitational waves propagating northward in the upperlayer may result in the development of the lower-layer vortex and precipitation.
EOF analysis has been conducted of the interdecadal variability of sea temperature anomaly fields at standard levels in the subsurface, and the abrupt change feature of sea temperature has been tested by use of movable t-test technique. A possible mechanism of the ocean-air system in the tropical Pacific is investigated by using the subsurface temperature, heat storage and wind stress data, leading to the main results as follows.
The analysis indicates that around 1980 there occurs a significant interdecadal abrupt change of temperature from sea surface to different depths, of which 4 modes show the accident and their formation is closely related to the southwestward subduction route of North Pacific sea temperature anomalies. The interdecadal signal of subduction in the window region of the North Pacific propagates southwestward to the subtropics, meeting the anomalous signal which propagates northeastward from the western Pacific at ~ 160-meter level in the thermocline. Therefore, the influence of the former on ENSO interdecadal variability might be indirect while the latter plays a more important role.
The western tropical South Pacific, which displays evident interdecadal variability, is the key region of the ENSO interdecadal variability. The positive temperature anomaly will move to the mid-tropical Pacific and the atmospheric response will excite an anticyclonic wind stress to the east of Australia, which will lead to the generation of a negative temperature anomaly in the tropical southwest Pacific. A similar evolution with an opposite sign will follow subsequently. The whole cycle takes about 13 years to complete.
KEYWORDS: Convection, Environmental sensing, Troposphere, Data centers, Humidity, Climatology, Information science, Information technology, Observatories, Floods
In the context of daily rainfall from 58 stations in South China and day-to-day gridded reanalysis from NCEP/NCAR, study is performed of April-June precipitation features at different time intervals in the research area in relation to the establishment of summer monsoon in the South-China Sea (SCS). Results show that the rainfall consists of frontal and monsoon rainfall, the former occurring dominantly in April and the latter largely in June as its principal phase, indicating that the vapor transport, dynamic and thermal features vary greatly for both. Further analysis shows that the amount of the frontal precipitation bears an intimate relation to the time of monsoon onset. In the year of deficient frontal rainfall the Sri Lanka vortex appears earlier and spreads northwards, in combination with northward-advancing convective band from Sumatra to cause the Indo-Burma trough to be established, as well as the subtropical high-pressure belt to break and eastward retreat - all happen earlier than usual, a situation that favors the establishment of westerlies in the SCS, leading to earlier establishment of SCS summer monsoon. In years of plentiful frontal rainfall, however, the formation of the Bengal Bay trough depends mainly on the displacement of Sumatra convection into the Indo-China peninsula, a situation unfavorable for the earlier breaking of the subtropical high-pressure belt and its eastward movement, resulting in later establishment of west winds in the SCS, so that SCS summer monsoon has its establishment delayed.
Based on TBB data from GMS of Japan, NCEP/NCAR reanalysis data and precipitation data from CPC Merged Analysis of Precipitation (CMAP), an investigation is carried out of seasonal changes of precipitation and convection over Asian-Australian "land bridge" areas and its possible factors. The results show that the precipitation and convection over Sumatra take on clearly seasonal changes with abundant (less) rainfall in winter (summer). The convection over Sumatra moves northwestward rapidly along "land bridge" in the late-April and the early-May (the 25th pentad) and the rainfall shows similar variations. It is the rapid northwestward shifting of convection that affects directly the subsequent enhancement of the convection over Indo-China Peninsula (ICP) area followed by the rupture of the subtropical high (SH) bands in this region leading to South China Sea (SCS) summer monsoon establishment. The zonal wind at lower troposphere in the equatorial Indian Ocean and the cross equatorial flow in 105°E are the main factors associated with the rapid northwestward shifting of convection along "land bridge".
Based on NCEP/NCAR reanalysis data, an investigation has been carried of climatic features of East Asian subtropical summer monsoon trough (sub-trough) and its comparison to South China Sea summer monsoon trough (SCS trough). The results show that the SCS trough is stronger than the sub-trough, whether convergence or convection. The sub-trough extends to higher level and inclines northward with altitude, but the SCS trough is reversed. The SCS trough onsets early and abruptly with the positive relative vorticity appearing suddenly and retreats slowly, but the sub-trough establishes step by step with the positive relative vorticity over Yunnan and Guizhou tableland and Guangxi areas spreading northeastward and withdraws rapidly. It is an obvious indicator that the easterly reverses the westerly during the SCS trough's onset, but the sub-trough establishment is characteristic of the westerly enhancement. The sub-trough has clearly frontal property, but the SCS trough is opposite.
Northwestern China is a semi-arid or arid area in China. Ningnan (or South Ningxia) district is located south of Ningxia Province belong to Northwestern part of China. Climate in this region is more dry and lack of precipitation. Because global climate have been changing, temperature has been increasing and rainfall has been decreasing in South Ningxia. The ecology has been deteriorating, such as vegetation cover destroying, water losing and soil erosion. Therefore, the people who live in South Ningxia have been poor. Recently, Chinese government put into effect on strategy of "great development of Chinese northwest", aiming to improve environmental and ecological conditions and rise people's living standard. South Ningxia district was defined as area of emigration where the measurements of returning land for farming to forestry were taken into account . How to evaluate the plans and measurements is very important to continue to improving local environmental and ecological conditions further. The basic index of evaluation is soil water profit and loss statement while evapotranspiration (ET) is an important component in statement income and outcome of soil water. It is a very complicated problem to estimate evapotranspiration (ET) over large area of natural surface. In this paper, the natural surface was classified as 5 categories based on information from remote sensing, each categories being dealt with special way. Using data of remote sensing and weather stations, the result of regional evapotranspiration over Ningnan(South Ningxia) was given out, and verified and discussing are also made out. The work helps to assess whether or not improve environmental and ecological conditions.
Using CMAP, daily observatory rainfall data and NCEP/NCAR reanalysis data, climatic features of moisture transport and its differences between flood years and drought years during the first rainy season of South China (SC) are discussed. Results show that moisture transport influencing South China exhibit distinct difference before South China Sea Summer Monsoon (SCSSM) onset and after SCSSM onset. Therefore the first rainy season of SC should be divided into two stages: from April to SCSSM onset and from SCSSM to June. Variations of moisture transport from the West Pacific and North China have important effects on flood or drought of SC. But that from Arabian Sea-Bay of Bangle mainly influences local rainfall instead of abnormal rainfall over SC.
The high quality dataset from the South China Sea (SCS) Monsoon Experiment and 40-year NCEP/NCAR reanalysis data are used to investigate the large scale features and abrupt change in meteorological elements during the onset of the SCS summer monsoon. It is found that the SCS summer monsoon establishment is characterized by the South Asian High migrating swiftly from the eastern side of Philippines to the northern part of Indo-China Peninsula and the enhancement of the Bay of Bengal trough and equatorial westerly over the Indian Ocean associated with the equatorial westerly expanding towards northeastward, and followed by the mid-low latitude interaction and continuous retreat eastward of the western Pacific subtropical high. Numerical results reveal that the Indial Peninsula acts as a critical role for the enhancement of the Bay of Bengal trough with a cyclonic difference circulation excited to the east side of the peninsula through ground sensible heating in such a way that the SCS summer monsoon occurs prior to the Indian summer monsoon.
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