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Hua L.,University of Chinese Academy of Sciences | Zhong L.,CAS Institute of Atmospheric Physics | Ke Z.,Laboratory for Climate Studies
International Journal of Climatology | Year: 2016

Dynamic recycling model (DRM) and reanalysis data were used to study the interaction between the land surface and atmosphere during the warm season from 1979 to 2010 across the arid and semi-arid regions of China. The nonlinear trends common to the key land-atmosphere interaction variables were extracted. For the whole study region, the precipitation recycling ratio showed an increasing trend, especially in the period before the 1990s. Simultaneously, increasing trends were also found in variables regionally related to precipitation, such as soil moisture, evaporation, precipitation efficiency, low-level cloud and precipitable water. However, the moisture transport due to westerly moisture flux showed a remarkable weakening throughout the whole study region. Based on significantly positive correlation between the precipitation efficiency and precipitation recycling ratio under relatively low moisture advection, it was concluded that the precipitation recycling process should not been ignored, for both direct and indirect precipitation processes, in the study region. The spatial patterns of nonlinear trends in land-atmosphere interaction variables indicated reverse tendencies in two sub-regions divided by the meridional boundary at approximately 110°E. For the western sub-region, although decreasing westerly moisture flow was found, the strengthening southerly moisture flux mainly resulted in an increase of precipitable water. Positive relationships among precipitable water, low cloud, precipitation, soil moisture, evaporation and the precipitation recycling ratio were also found. The soil becoming wetter and the precipitation recycling process becoming enhanced suggested the existence of positive land-atmosphere interaction in the western sub-region. However, the opposite tendencies were found in the eastern sub-region, where a weakening of advected moisture convergence was caused by decreases in both westerly and southerly moisture transport. Furthermore, less evaporation and warming temperatures suggested the climate in the eastern sub-region shifted towards relatively warmer and drier conditions throughout the course of the study period. © 2016 Royal Meteorological Society. Source

Ren F.,Laboratory for Climate Studies | Liang J.,Nanjing University | Wu G.,CAS Institute of Atmospheric Physics | Dong W.,Beijing Normal University | Yang X.,Nanjing University
Journal of Climate | Year: 2011

Data homogeneity has become a significant issue in the study of tropical cyclones (TCs) and climate change. In this study, three historical datasets for the western North Pacific TCs from the Joint Typhoon Warning Center (JTWC), Japan Meteorological Agency (JMA), and China Meteorological Administration (CMA) are compared with a focus on TC intensity. Over the past 55 years (1951-2005), significant discrepancies are found among the three datasets, especially between the CMA and JTWC datasets. The TC intensity in the CMA dataset was evidently overestimated in the 1950s and from the late 1960s to the early 1970s, while it was overestimated after 1988 in the JTWC dataset, especially during 1993-2003. Large discrepancies in TC tracks exist in two periods of 1951-early 1960s and 1988-1990s. Further analysis reveals that the discrepancies are obviously related to the TC observational techniques. Before the era of meteorological satellites (1951-the early 1960s), and after the termination of aircraft reconnaissance (since 1988), large discrepancies exist in both TC intensity and track. That the intensity discrepancy was smallest during the period (1973-87) when aircraft reconnaissance data and the Dvorak technique were both available suggests that availability of the aircraft reconnaissance and the Dvorak method helps in reducing the TC intensity discrepancy. For those TCs that were included in all the three datasets, no significant increasing or decreasing trend was found over the past 50 years. Each of the three TC datasets has individual characteristics that make it difficult to tell which one is the best. For TCs that affect China, the CMA dataset has obvious advantages such as more complete and more accurate information. © 2011 American Meteorological Society. Source

Peng Y.,Xian Jiaotong University | Shen C.,Yunnan Normal University | Shen C.,Albany State University | Cheng H.,Xian Jiaotong University | And 2 more authors.
Climate of the Past | Year: 2014

We use proxy data and modeled data from 1000 year model simulations with a variety of climate forcings to examine the occurrence of severe event of persistent drought over eastern China during the last millennium and diagnose the mechanisms. Results show that the model was able to roughly simulate most of these droughts over the study area during the last millennium such as those that occurred during the periods of 1123-1152, 1197-1223, 1353-1363, 1428-1449, 1479-1513, and 1632-1645. Our analyses suggest that these six well-captured droughts may caused by the East Asian summer monsoon (EASM) weakening. Study on the wavelet transform and spectral analysis reveals these events occurred all at the statistically significant 15-35-year timescale. A modeled data intercomparison suggests the possibility that solar activity may be the primary driver in the occurrence of the 1129-1144, 1354-1365, 1466-1491 and 1631-1648 droughts as identified by the model. However another possibility that these events may be related to internal variability cannot be excluded. Although the El Niño-Southern Oscillation (ENSO) plays an important role in monsoon variability, a temporally consistent relationship between the droughts and SST pattern in the Pacific Ocean could not be found either in the modeled or proxy data. Our analyses also indicate that large volcanic eruptions play a role as an amplifier in the drought of 1631-1648 and caused the droughts of 1830-1853 and 1958-1976, which was identified by the model. © Author(s) 2014. Source

Ren H.-L.,University of Hawaii at Manoa | Ren H.-L.,Laboratory for Climate Studies | Jin F.-F.,University of Hawaii at Manoa | Gao L.,University of Hawaii at Manoa | Gao L.,Laboratory for Climate Studies
Journal of the Atmospheric Sciences | Year: 2012

A method of eddy structure decomposition is proposed to detect how low-frequency flow associated with the North Atlantic Oscillation (NAO) organizes systematically synoptic eddy (SE) activity to generate inphase and upstream feedbacks. In this method, a statistical eddy streamfunction (SES) field, defined by the three-point covariance of synoptic-scale streamfunction, is introduced to characterize spatiotemporal SE flow structures. The SES field is decomposed into basic and anomalous parts to represent the climatological SE flow structure and its departure. These two parts are used to calculate the basic and anomalous eddy velocity, eddy vorticity, and thus eddy vorticity flux fields, in order to elucidate those two SE feedbacks onto the NAO. This method is validated by the fact that the observed anomalous eddy vorticity flux field can be reproduced well by two linear terms: the basic eddy velocity field multiplied by anomalous eddy vorticity field and the anomalous eddy velocity field multiplied by basic eddy vorticity field. With this method, it is found that, in the positive and negative phases, the NAO flow tends to induce two different types of anomalous SE flow structure, which are largely responsible for generating the net meridional and zonal eddy vorticity fluxes that, in return, feed back onto the NAO. The two processes that are related to these two different types dominate in the in-phase and upstream feedbacks, which are delineated conceptually into two kinematic mechanisms associated with zonal-slanting and meridional-shifting changes in the SE structure. The present observational evidence supports the theory of eddy-induced instability for low-frequency variability and also provides insights into the reason for the asymmetry between the SE feedbacks onto the two NAO phases. © 2012 American Meteorological Society. Source

Wu J.,Laboratory for Climate Studies | Gao X.-J.,Laboratory for Climate Studies
Chinese Journal of Geophysics (Acta Geophysica Sinica) | Year: 2013

A new gridded daily dataset with the resolution of 0.25° latitude by 0.25° longitude, CN05.1, is constructed for the purpose of high resolution climate model validation over China region. The dataset is based on the interpolation from over 2400 observing stations in China, includes 4 variables: daily mean, minimum and maximum temperature, daily precipitation. The "anomaly approach" is applied in this interpolation. The climatology is first interpolated by thin-plate smoothing splines and then a gridded daily anomaly derived from angular distance weighting method is added to climatology to obtain the final dataset. Intercomparison of the dataset with other three daily datasets, CN05 for temperature, and EA05 and APHRO for precipitation is conducted. The analysis period is from 1961 to 2005. For multi-annual mean temperature variables, results show small differences over eastern China with dense observation stations, but larger differences (warmer) over western China with less stations between CN05.1 and CN05. The temperature extremes are measured by TX3D (mean of the 3 greatest maximum temperatures in a year) and TN3D (mean of the 3 lowest minimum temperatures). CN05.1 in general shows a warmer TX3D over China, while a lower TN3D in the east and greater TN3D in the west are found compared to CN05. A greater value of annual mean precipitation compared to EA05 and APHRO, especially to the latter, is found in CN05.1. For precipitation extreme of R3D (mean of the 3 largest precipitations in a year), CN05.1 presents lower value of it in western China compared to EA05. Source

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