The western North Pacific subtropical high(WNPSH) dominates the summer climate over East Asia. The intensity,position, and shape of WNPSH influence the spatiotemporal distributions of precipitation, temperature, and t...The western North Pacific subtropical high(WNPSH) dominates the summer climate over East Asia. The intensity,position, and shape of WNPSH influence the spatiotemporal distributions of precipitation, temperature, and tropical cyclone activities in this region. This paper intends to investigate the performance of the UK Met Office Global Seasonal forecast system version 5(GloSea5) in simulation/prediction of the WNPSH based on a hindcast dataset. Analyses of the hindcast data show a systematic bias in the mean circulation over West Pacific, with negative geopotential height anomalies over the western North Pacific(WNP) and cyclonic anomalies in the 850-hPa winds and water vapor transport, indicating a weakening and eastward shift of the WNPSH. Despite the model’s bias in the climatology, it well captured the interannual variability of the monthly and seasonal-mean intensity of the WNPSH and the position of its ridge line in boreal summer from 1993 to 2015. The seasonal hindcasts indicate that there is significant prediction skill at up to three-month lead time for both the intensity and position of the WNPSH ridge line. The relationship between the WNPSH and different phases of the El Nino–Southern Oscillation(ENSO) in both the observational data and GloSea5 hindcasts was then investigated. The model captured the summer WNPSH anomalies well during most of the ENSO phases, except in the La Nina decaying and neutral summers. The intensity of the anticyclone in the WNP is weak in the decaying phase of El Nino in the GloSea5 hindcasts compared with the reanalysis data. GloSea5 is capable of representing the lagged teleconnection between El Nino events in the previous winter and the intensity of the WNPSH in the following summer. Regression analysis reveals weakened negative sea surface temperature anomalies(SSTAs) over the WNP in GloSea5, which reduced the gradient between the tropical western Pacific and the tropical Indian Ocean, resulting in a weaker easterly anomaly and stronger westerly anomaly, contributing t展开更多
Quantification of greenhouse gases[nitrous oxide(N_(2)O)and methane(CH_(4))]and nitric oxide(NO)emissions from subtropical conventional vegetable systems through multi-site field measurements are needed to obtain accu...Quantification of greenhouse gases[nitrous oxide(N_(2)O)and methane(CH_(4))]and nitric oxide(NO)emissions from subtropical conventional vegetable systems through multi-site field measurements are needed to obtain accurate regional and global estimates.N2 O,NO and CH4 emissions from subtropical conventional vegetable systems were simultaneously measured at two different sites with hilly topography in the Sichuan basin,southwest China by using the static chamber gas chromatography technique.Results showed that annual soil N_(2)O and NO fluxes for the treatment receiving N fertilizer ranged from 6.34-7.71 kg N ha^(-1) yr^(-1) and 0.69-0.85 kg N ha^(-1) yr^(-1),respectively,while decreased soil CH4 uptakes by 26.4%as compared with no N fertilizer addition across our two sites of experiment.Overall,the average direct N2 O and NO emission factor(EFd)were 0.71%and 0.12%,respectively,which were both lower than the available EFd for subtropical conventional vegetable systems.This finding indicates that current regional and global estimates of N_(2)O and NO emissions from vegetable fields are likely overestimated.Background N_(2)O emissions(3.42-3.62 kg N ha^(-1) yr^(-1))from the subtropical conventional vegetable systems were relatively high as compared with available field measurements worldwide,suggesting that background N_(2)O emissions cannot be ignored for regional estimate of N_(2)O emissions in subtropical region.Nevertheless,the significantly intra-and inter-annual variations in N_(2)O,CH_(4) and NO emissions were also observed in the present study,which could be explained by temporal variations of environmental variables(i.e.soil temperature and moisture).The differences in N_(2)O and NO EFd and CH_(4)emissions between various vegetable systems in particular under subtropical conditions should be taken into account when compiling regional or global inventories and proposing mitigation practices.展开更多
In this paper, characteristics of precipitating clouds in a thermal convective system （TCS） occurred in the southeastern mainland of China at 15：00 BT （Beijing time） on August 2, 2003 in the central western subtr...In this paper, characteristics of precipitating clouds in a thermal convective system （TCS） occurred in the southeastern mainland of China at 15：00 BT （Beijing time） on August 2, 2003 in the central western subtropical Pacific anticyclone （WSPA） is studied by using TRMM tropical rainfallmeasuring mission PR （precipitution radar） and IR Infrared radiation measurements. The precipitating cloud structures in both horizontal and vertical, relationship among storm top, cloud top, and surface rain rate are particularly analyzed. Results show that a strong ascending air at 500 hPa and a strong convergence of moisture flux at 850 hPa in the central WSPA supply necessary conditions both in dynamics and moisture for the happening of the TCS precipitation. The TRMM PR observation shows that the horizontal scale of the most TCS precipitating clouds is about 30-40 kin, their averaged vertical scale is above 10 kin, and the maximum reaches 17.5 kin. The maximum rain rate near surface of those TCS clouds is beyond 50 mm h^-1. The mean rain profile of the TCS clouds shows that its maximum rain rate at 5 km altitude is i km lower than the estimated freezing level of the environment. Compared with the mesoscale convective system （MCS） of ＂98.7.20＂, both systems have the same altitude of the maximum rain rate displayed from both mean rain profiles, but the TCS is much deeper than the MCS. From the altitude of the maximum rain rate to near surface, profiles show that rain rate reducing in the TCS is faster than that in the MCS, which implies a strong droplet evaporation process occurring in the TCS. Relationship among cloud top, storm top, and surface rain rate analysis indicates a large variation of cloud top when storm top is lower. On the contrary, the higher the storm top, the more consistent both cloud top and storm top. And, the larger the surface rain rate, the higher and more consistent for both cloud top and storm top. At the end, results expose that area fractions of non-precipitating clouds and c展开更多
基金Supported by the National Key Research and Development Program of China(2017YFC1502303)National Natural Science Fundation of China(41730964,41975091,and 41605078)UK–China Research and Innovation Partnership Fund through the Met Office Climate Science for Service Partnership(CSSP)China as part of the Newton Fund。
文摘The western North Pacific subtropical high(WNPSH) dominates the summer climate over East Asia. The intensity,position, and shape of WNPSH influence the spatiotemporal distributions of precipitation, temperature, and tropical cyclone activities in this region. This paper intends to investigate the performance of the UK Met Office Global Seasonal forecast system version 5(GloSea5) in simulation/prediction of the WNPSH based on a hindcast dataset. Analyses of the hindcast data show a systematic bias in the mean circulation over West Pacific, with negative geopotential height anomalies over the western North Pacific(WNP) and cyclonic anomalies in the 850-hPa winds and water vapor transport, indicating a weakening and eastward shift of the WNPSH. Despite the model’s bias in the climatology, it well captured the interannual variability of the monthly and seasonal-mean intensity of the WNPSH and the position of its ridge line in boreal summer from 1993 to 2015. The seasonal hindcasts indicate that there is significant prediction skill at up to three-month lead time for both the intensity and position of the WNPSH ridge line. The relationship between the WNPSH and different phases of the El Nino–Southern Oscillation(ENSO) in both the observational data and GloSea5 hindcasts was then investigated. The model captured the summer WNPSH anomalies well during most of the ENSO phases, except in the La Nina decaying and neutral summers. The intensity of the anticyclone in the WNP is weak in the decaying phase of El Nino in the GloSea5 hindcasts compared with the reanalysis data. GloSea5 is capable of representing the lagged teleconnection between El Nino events in the previous winter and the intensity of the WNPSH in the following summer. Regression analysis reveals weakened negative sea surface temperature anomalies(SSTAs) over the WNP in GloSea5, which reduced the gradient between the tropical western Pacific and the tropical Indian Ocean, resulting in a weaker easterly anomaly and stronger westerly anomaly, contributing t
基金the Major Science and Technology Program for Water Pollution Control and Treatment(Grant No.2017ZX07101001)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDA23090403)National Key Research and Development Program(Grant No.2019YFD1100503)。
文摘Quantification of greenhouse gases[nitrous oxide(N_(2)O)and methane(CH_(4))]and nitric oxide(NO)emissions from subtropical conventional vegetable systems through multi-site field measurements are needed to obtain accurate regional and global estimates.N2 O,NO and CH4 emissions from subtropical conventional vegetable systems were simultaneously measured at two different sites with hilly topography in the Sichuan basin,southwest China by using the static chamber gas chromatography technique.Results showed that annual soil N_(2)O and NO fluxes for the treatment receiving N fertilizer ranged from 6.34-7.71 kg N ha^(-1) yr^(-1) and 0.69-0.85 kg N ha^(-1) yr^(-1),respectively,while decreased soil CH4 uptakes by 26.4%as compared with no N fertilizer addition across our two sites of experiment.Overall,the average direct N2 O and NO emission factor(EFd)were 0.71%and 0.12%,respectively,which were both lower than the available EFd for subtropical conventional vegetable systems.This finding indicates that current regional and global estimates of N_(2)O and NO emissions from vegetable fields are likely overestimated.Background N_(2)O emissions(3.42-3.62 kg N ha^(-1) yr^(-1))from the subtropical conventional vegetable systems were relatively high as compared with available field measurements worldwide,suggesting that background N_(2)O emissions cannot be ignored for regional estimate of N_(2)O emissions in subtropical region.Nevertheless,the significantly intra-and inter-annual variations in N_(2)O,CH_(4) and NO emissions were also observed in the present study,which could be explained by temporal variations of environmental variables(i.e.soil temperature and moisture).The differences in N_(2)O and NO EFd and CH_(4)emissions between various vegetable systems in particular under subtropical conditions should be taken into account when compiling regional or global inventories and proposing mitigation practices.
基金Supported by grants of NKBRDPC (No. 2004CB418304) NSFC (Nos. 40175015 and 40375018)NSFC grant of the Joint Research Fund for Overseas Chinese Young Scholars (No. 40428006)EORC/JAXA (No. 206)
文摘In this paper, characteristics of precipitating clouds in a thermal convective system （TCS） occurred in the southeastern mainland of China at 15：00 BT （Beijing time） on August 2, 2003 in the central western subtropical Pacific anticyclone （WSPA） is studied by using TRMM tropical rainfallmeasuring mission PR （precipitution radar） and IR Infrared radiation measurements. The precipitating cloud structures in both horizontal and vertical, relationship among storm top, cloud top, and surface rain rate are particularly analyzed. Results show that a strong ascending air at 500 hPa and a strong convergence of moisture flux at 850 hPa in the central WSPA supply necessary conditions both in dynamics and moisture for the happening of the TCS precipitation. The TRMM PR observation shows that the horizontal scale of the most TCS precipitating clouds is about 30-40 kin, their averaged vertical scale is above 10 kin, and the maximum reaches 17.5 kin. The maximum rain rate near surface of those TCS clouds is beyond 50 mm h^-1. The mean rain profile of the TCS clouds shows that its maximum rain rate at 5 km altitude is i km lower than the estimated freezing level of the environment. Compared with the mesoscale convective system （MCS） of ＂98.7.20＂, both systems have the same altitude of the maximum rain rate displayed from both mean rain profiles, but the TCS is much deeper than the MCS. From the altitude of the maximum rain rate to near surface, profiles show that rain rate reducing in the TCS is faster than that in the MCS, which implies a strong droplet evaporation process occurring in the TCS. Relationship among cloud top, storm top, and surface rain rate analysis indicates a large variation of cloud top when storm top is lower. On the contrary, the higher the storm top, the more consistent both cloud top and storm top. And, the larger the surface rain rate, the higher and more consistent for both cloud top and storm top. At the end, results expose that area fractions of non-precipitating clouds and c
