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Huang X.,Peking University | Huang X.,Institute for Climate and Global Change Research | Huang X.,Nanjing University | Huang X.,Jiangsu Collaborative Innovation Center for Climate Change | And 5 more authors.
Journal of Climate | Year: 2015

The direct radiative effect (DRE) of multiple aerosol species [sulfate, nitrate, ammonium, black carbon (BC), organic carbon (OC), and mineral aerosol] and their spatiotemporal variations over China were investigated using a fully coupled meteorology-chemistry model [Weather Research and Forecasting (WRF) Model coupled with Chemistry (WRF-Chem)] for the entire year of 2006. This study made modifications to improve the model performance, including updating land surface parameters, improving the calculation of transition-metal-catalyzed oxidation of SO2, and adding heterogeneous reactions between mineral dust aerosol and acid gases. The modified model generally reproduced the magnitude, seasonal pattern, and spatial distribution of the measured meteorological conditions, concentrations of PM10 and its components, and aerosol optical depth (AOD), although some low biases existed in modeled aerosol concentrations. A diagnostic iteration method was used to estimate the overall DRE of aerosols and contributions from different components. At the land surface, the incident net radiation flux was reduced by 10.2 W m-2 over China. Aerosols significantly warmed the atmosphere with the national mean DRE of +10.8 W m-2. BC was the leading radiative heating component (+8.7 W m-2), followed by mineral aerosol (+1.1W m-2). At the top of the atmosphere (TOA), BC introduced the largest radiative perturbation (+4.5W m-2), followed by sulfate (-1.4W m-2). The overall perturbation of aerosols on radiation transfer is quite small over China, demonstrating the counterbalancing effect between scattering and adsorbing aerosols. AerosolDREat theTOAhad distinct seasonality, generally with a summer maximum and winter minimum, mainly determined by mass loadings, hygroscopic growth, and incident radiation flux. © 2015 American Meteorological Society.

Chang H.-L.,Central Weather Bureau | Chang H.-L.,National Central University | Yang S.-C.,National Central University | Yuan H.,Nanjing University | And 3 more authors.
Monthly Weather Review | Year: 2015

Measurement of the usefulness of numerical weather prediction considers not only the forecast quality but also the possible economic value (EV) in the daily decision-making process of users. Discrimination ability of an ensemble prediction system (EPS) can be assessed by the relative operating characteristic (ROC), which is closely related to the EV provided by the same forecast system. Focusing on short-range probabilistic quantitative precipitation forecasts (PQPFs) for typhoons, this study demonstrates the consistent and strongly related characteristics of ROC and EV based on the Local Analysis and Prediction System (LAPS) EPS operated at the Central Weather Bureau in Taiwan. Sensitivity experiments including the effect of terrain, calibration, and forecast uncertainties on ROC and EV show that the potential EV provided by a forecast system is mainly determined by the discrimination ability of the same system. The ROC and maximum EV (EVmax) of an EPS are insensitive to calibration, but the optimal probability threshold to achieve the EVmax becomes more reliable after calibration. In addition, the LAPS ensemble probabilistic forecasts outperform deterministic forecasts in respect to both ROC and EV, and such an advantage grows with increasing precipitation intensity. Also, even without explicitly knowing the cost-loss ratio, one can still optimize decision-making and obtain the EVmax by using ensemble probabilistic forecasts. © 2015 American Meteorological Society.

Zhang N.,Nanjing University | Zhang N.,Jiangsu Collaborative Innovation Center for Climate Change | Gao Z.,CAS Institute of Atmospheric Physics | Liu Y.,Brookhaven National Laboratory | Li D.,Princeton University
Journal of Geophysical Research Atmospheres | Year: 2015

The critical bulk Richardson number (Ricr) is an important parameter in planetary boundary layer (PBL) parameterization schemes used in many climate models. This paper examines the sensitivity of a global climate model, the Beijing Climate Center atmospheric general circulation model, to Ricr. The results show that the simulated global average of PBL height increases nearly linearly with Ricr, with a change of about 114 m for a change of 0.5 in Ricr. The surface sensible (latent) heat flux decreases (increases) as Ricr increases. The influence of Ricr on surface air temperature and specific humidity is not significant. The increasing Ricr may affect the location of the Westerly Belt in the Southern Hemisphere. Further diagnosis reveals that changes in Ricr affect stratiform and convective precipitations differently. Increasing Ricr leads to an increase in the stratiform precipitation but a decrease in the convective precipitation. Significant changes of convective precipitation occur over the Intertropical Convergence Zone, while changes of stratiform precipitation mostly appear over arid land such as North Africa and Middle East. © 2015. American Geophysical Union. All Rights Reserved.

Sun R.,Nanjing University | Yuan H.,Nanjing University | Yuan H.,Jiangsu Collaborative Innovation Center for Climate Change | Liu X.,Anhui Agricultural University | Jiang X.,Nanjing University
Journal of Hydrology | Year: 2016

Satellite-gauge quantitative precipitation estimate (QPE) products may reduce the errors in near real-time satellite precipitation estimates by combining rain gauge data, which provides great potential to hydrometeorological applications. This study aims to comprehensively evaluate four of the latest satellite-gauge QPEs, including NASA's Tropical Rainfall Measuring Mission (TRMM) 3B42V7 product, NOAA's Climate Prediction Center (CPC) MORPHing technique (CMORPH) bias-corrected product (CMORPH CRT), CMORPH satellite-gauge merged product (CMORPH BLD) and CMORPH satellite-gauge merged product developed at the National Meteorological Information Center (NMIC) of the China Meteorological Administration (CMA) (CMORPH CMA). These four satellite-gauge QPEs are statistically evaluated over the Huaihe River basin during 2003-2012 and applied into the distributed Variable Infiltration Capacity (VIC) model to assess hydrologic utilities.Compared to the China Gauge-based Daily Precipitation Analysis (CGDPA) newly developed at CMA/NMIC, the four satellite-gauge QPEs generally depict the spatial distribution well, with the underestimation in the southern mountains and overestimation in the northern plain of the Huaihe River basin. Specifically, both TRMM and CMORPH CRT adopt simple gauge adjustment algorithms and exhibit relatively poor performance, with evidently deteriorated quality in winter. In contrast, the probability density function-optimal interpolation (PDF-OI) gauge adjustment procedure has been applied in CMORPH BLD and CMORPH CMA, resulting in higher quality and more stable performance. CMORPH CMA further benefits from a merged dense gauge observation network and outperforms the other QPEs with significant improvements in rainfall amount and spatial/temporal distributions. Due to the insufficient gauge observations in the merging process, CMORPH BLD features the similar error characteristics of CMORPH CRT with a positive bias of light precipitation and a negative bias of heavy precipitation, in contrast to the overall large overestimation by TRMM. The quality of QPEs directly impacts streamflow simulations, as the precipitation biases are propagated into simulated streamflow through interaction with hydrologic processes. The general streamflow pattern is well captured at multiple time scales by the simulations using the four satellite-gauge QPEs as the input forcing. CMORPH CRT shows the worst simulations in both long-term streamflow and extreme flood events, while CMORPH CMA forced streamflow simulations even outperform that forced by CGDPA. CMORPH CMA is able to reproduce the July 2003 flood event, while the other three QPEs fail to generate such extreme flood. Overall, CMORPH CMA shows great potential to improve the precipitation distribution and hydrometeorological simulations, and can serve as an alternative high quality QPE in China. © 2016 Elsevier B.V.

Guo Y.,Sun Yat Sen University | Wen Z.,Sun Yat Sen University | Wen Z.,Jiangsu Collaborative Innovation Center for Climate Change | Wu R.,CAS Institute of Atmospheric Physics
Journal of Climate | Year: 2016

The leadingmode of boreal spring precipitation variability over the tropical Pacific experienced a pronounced interdecadal change around the late 1990s. The pattern before 1998 features positive precipitation anomalies over the equatorial eastern Pacific (EP) with positive principle component years. The counterpart after 1998 exhibits a westward shift of the positive center to the equatorial central Pacific (CP). Observational evidence shows that this interdecadal change in the leading mode of precipitation variability is closely associated with a distinctive sea surface temperature (SST) anomaly pattern. The westward shift of the anomalous precipitation center after 1998 is in tandemwith a similar shift of maximumwarming from the EP to CP.Diagnostic analyses based on a linear equation of themixed layer temperature anomaly exhibit that an interdecadal enhancement of zonal advection (ZA) feedback process plays a vital role in the shift in the leading mode of both the tropical Pacific SST and the precipitation anomaly during spring. Moreover, the variability of the anomalous zonal current at the upper ocean dominates the ZA feedback change, while the mean zonal SST gradient associated with a La Niña-like pattern of the mean state only accounts for a relatively trivial proportion of the ZA feedback change. It was found that both the relatively rapid decaying of the SST anomalies in the EP and the La Niña-like mean state make it conceivable that the shift of the leading mode of the tropical precipitation anomaly only occurs in spring. In addition, the largest variance of the anomalous zonal current in spring might contribute to the unique interdecadal change in the tropical spring precipitation anomaly pattern. © 2016 American Meteorological Society.

Chen Z.,Sun Yat Sen University | Wen Z.,Sun Yat Sen University | Wen Z.,Chinese Academy of Meteorological Sciences | Wen Z.,Jiangsu Collaborative Innovation Center for Climate Change | And 3 more authors.
Climate Dynamics | Year: 2015

This study investigates the relative importance of tropical Indian Ocean warming (IOW) and equatorial central to eastern Pacific cooling (EPC) in sustaining an anomalous Western North Pacific anticyclone (WNPAC) during the transition from an El Niño in the preceding winter to a La Niña in the subsequent summer through a suite of numerical experiments. The numerical results indicate that the WNPAC is maintained by a combined effect of IOW and EPC during the La Niña developing years. The contribution of IOW in maintaining the WNPAC sustains from spring to early summer, but appears to weaken after that as IOW decays. The role of IOW is via an eastward-propagating Kelvin wave induced Ekman divergence mechanism. The decay of IOW is because of reduction in downward solar radiation associated with above normal precipitation in situ. As the cooling develops over central to eastern Pacific from spring to summer, EPC starts to contribute to the maintenance of the WNPAC during summer through stimulating a Rossby wave response to its northwest. In this study, we have identified that the cooling over the central to eastern Pacific plays an important role in sustaining the WNPAC during La Niña developing summers. This finding may help improve the prediction of the East Asian summer monsoon, which is closely associated with the WNPAC. © 2015 Springer-Verlag Berlin Heidelberg

Wang J.,Sun Yat Sen University | Wang J.,State University of New York at Stony Brook | Wen Z.,Sun Yat Sen University | Wen Z.,Chinese Academy of Meteorological Sciences | And 3 more authors.
Climate Dynamics | Year: 2016

A pronounced summer rainfall increase over southern China occurred around 1992/1993. In the present study, the impact of the boreal summer intraseasonal oscillation (BSISO) on this decadal increase is investigated through diagnostic analysis. It is found that the BSISO-induced rainfall increase accounts for approximately 17.4% of the observed decadal rainfall increase, with a primary part coming from changes in the rainfall pattern associated with phases 3–5 of the BSISO. A further analysis reveals that changes in rainfall pattern over southern China are mainly ascribed to changes in spatial structure of anomalous convection associated with interdecadal change in BSISO tracks. Apart from significant influence of changes in BSISO tracks, changes in the frequency of individual active BSISO phases also have considerable influence on the interdecadal change in summer rainfall over southern China. Based on our analysis, the increase in absolute and relative frequency of occurrence of phases 1 and 8, coupled with their corresponding rainfall pattern, makes a positive contribution to the increase in southern China summer rainfall. The interdecadal change in the BSISO tracks and the frequency of active BSISO phases is likely related to coherent changes in atmospheric circulation and sea surface temperature over the Indian Ocean and the western Pacific. © 2016 Springer-Verlag Berlin Heidelberg

Zhang H.,Sun Yat Sen University | Wen Z.,Sun Yat Sen University | Wen Z.,Jiangsu Collaborative Innovation Center for Climate Change | Wu R.,CAS Institute of Atmospheric Physics | And 2 more authors.
Climate Dynamics | Year: 2016

Previous studies have revealed inter-decadal changes in the East Asian summer monsoon (EASM) that occurred around the late 1970s and early 1990s, respectively. The present study compares characteristics of these two changes and analyzes plausible influences of the South Indian Ocean (SIO) sea surface temperature (SST) change. The two changes share pronounced common features, characterized by an equivalent barotropic circulation anomaly over northern East Asia and a meridional vertical overturning circulation over the tropical region. Meanwhile, they display some distinct characteristics, especially over the tropics. The circumfluent anomalies are more robust for the first change than for the second one. Related amplitude asymmetry is partly attributed to a weakening trend in the EASM. Moreover, SST change in the SIO, featuring a decadal warming since the 1980s and a cooling after 1993, may contribute to both of these inter-decadal changes. Cold SST anomaly induces anomalous mid-tropospheric descent over the western SIO and ascent extending from the eastern SIO to western Australia and over the equatorial Indian Ocean. The accompanying upper-tropospheric divergent flows from western Australia and equatorial Indian Ocean to the Philippines lead to anomalous descent and an anomalous lower-tropospheric anticyclone over the South China Sea–Philippines. Warm SST anomaly induces opposite changes in above regions. The possible influence of SST anomaly in the SIO is further confirmed by numerical experiments. © 2016 Springer-Verlag Berlin Heidelberg

Zou X.,National Climate Center | Ren F.,Chinese Academy of Meteorological Sciences | Ren F.,Jiangsu Collaborative Innovation Center for Climate Change
Advances in Atmospheric Sciences | Year: 2015

A new technique for identifying regional climate events, the Objective Identification Technique for Regional Extreme Events (OITREE), was applied to investigate the characteristics of regional heavy rainfall events in China during the period 1961–2012. In total, 373 regional heavy rainfall events (RHREs) were identified during the past 52 years. The East Asian summer monsoon (EASM) had an important influence on the annual variations of China’s RHRE activities, with a significant relationship between the intensity of the RHREs and the intensity of the Mei-yu. Although the increase in the frequency of those RHREs was not significant, China experienced more severe and extreme regional rainfall events in the 1990s. The middle and lower reaches of the Yangtze River and the northern part of South China were the regions in the country most susceptible to extreme precipitation events. Some stations showed significant increasing trends in the southern part of the middle and lower reaches of the Yangtze River and the northern part of South China, while parts of North China, regions between Guangxi and Guangdong, and northern Sichuan showed decreasing trends in the accumulated intensity of RHREs. The spatial distribution of the linear trends of events’ accumulated intensity displayed a similar so-called “southern flooding and northern drought” pattern over eastern China in recent decades. © 2015, Chinese National Committee for International Association of Meteorology and Atmospheric Sciences, Institute of Atmospheric Physics, Science Press and Springer-Verlag Berlin Heidelberg.

Shi J.,Nanjing University | Shi J.,Jiangsu Collaborative Innovation Center for Climate Change | Lu H.,Nanjing University | Lu H.,Jiangsu Collaborative Innovation Center for Climate Change | And 6 more authors.
Global and Planetary Change | Year: 2015

February-April drought strongly affects agriculture and socio-economics in southeastern China, yet its long-term variability has not been assessed due to the shortness of instrumental records. In this study, we reported a 168-year tree-ring width chronology from a steep, low-elevation site with thin soil layers in the Xianxia Mountains, southeastern China. Contrary to the existing chronologies that are mostly temperature sensitive, this chronology contained a strong February-April precipitation signal, indicating great potential for tree-ring based precipitation reconstructions in southeastern China. The reconstruction explained 47.8% of the instrumental variance during 1951-2012. The full reconstruction indicated that there were 3 dry periods (1873-1896, 1924-1971, 1995-2012) and 2 wet periods (1856-1872, 1972-1994) during 1856-2013. The extreme drought in 2011 was not unprecedented for the past 168. years, and the recent severe droughts may be part of interdecadal variations in regional February-April precipitation. Our results also suggested that February-April precipitation in southeastern China was highly influenced by the tropical Pacific climate system, in particular El Niño-Southern Oscillation (ENSO). © 2015 Elsevier B.V.

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