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Soil moisture conditions affect energy partitioning between sensible and latent heat fluxes, resulting in a change in surface temperatures. In this study, the relationships between antecedent soil moisture conditions [as indicated by the 6-month standardized precipitation index (SPI)] and several temperature indices are statistically quantified using the quantile regression analysis across East China to investigate the influence of soil moisture on summer surface temperatures. These temperature indices include percentage of hot days (%HD), heat-wave duration (HWD), daily temperature range (DTR), and daily minimum temperature (Tmin). It was demonstrated that soil moisture had a significant impact on %HD and HWDat higher quantiles in all regions but the east, suggesting that drier soil moisture conditions tend to intensity summer hot extremes. It was also found that hot extremes (%HD and HWD at higher quantiles) had increased substantially from 1958 to 2010. Soil moisture also significantly affected the DTR in all regions but tended to have more impacts on the DTR in soil moisture-limited regimes than in energy-limited regimes. This study provides observational evidence of soil moisture influences on hot extremes in East China. [ABSTRACT FROM AUTHOR]

This paper combines observations, climatic analysis, and numerical modeling to investigate the Tibetan Plateau's (TP) surface heating conditions' influence on extreme persistent precipitation events (PEPEs) in southeastern China. Observations indicated an increase of TP surface air temperature 3-4 days prior to extreme persistent precipitation events in southeastern China. NCEP reanalysis data revealed a significant low pressure anomaly in southern China and a high pressure anomaly in northern China during extreme persistent precipitation event periods. Using correlation analysis and random resampling nonparametric statistics, a typical PEPE event from 17 to 25 June 2010 was selected for numerical simulation. The Weather Research and Forecasting (WRF) Model was used to investigate the impact of the TP's surface heating on the evolution of this event. Three contrasting WRF experiments were conducted with different surface heating strengths by changing initial soil moisture over the TP. Different soil conditions generate different intensities of surface sensible heat fluxes and boundary layer structures over the TP resulting in two main effects on downstream convective rainfall: modulating large-scale atmospheric circulations and modifying the water vapor transport at southern China. Increased surface heating in the TP strengthens a high pressure system over the Yangtze Plain, thereby blocking the northward movement of precipitation. It also enhances the water vapor transport from the South China Sea to southern China. The combined effects substantially increase precipitation over most of the southeastern China region. [ABSTRACT FROM AUTHOR]

Diurnal cycle of surface air temperature T is an important metric indicating the feedback of land-atmospheric interaction to global warming, whereas the ability of current reanalyses to reproduce its variation had not been assessed adequately. Here, we evaluate the daily maximum temperature Tmax, daily minimum temperature Tmin, and diurnal temperature range (DTR) in five reanalyses based on observations collected at 2253 weather stations over China. Our results show that the reanalyses reproduce Tmin very well; however, except for Modern-Era Retrospective Analysis for Research and Applications version 2 (MERRA-2), they substantially underestimate Tmax and DTR by 1.21°-6.84°8 over China during the period of 1980-2014. MERRA-2 overestimates Tmax and DTR by 0.35° and 0.81°C, which are closest with observation. The reanalyses are skillful in reproducing the interannual variability of Tmax and Tmin but relatively poor for DTR. All reanalyses underestimate the warming trend of Tmin by 0.13°-0.17°C(10 yr)-1 throughoutChina during 1980-2014, and underestimate the warming trend of Tmax by 0.24°-0.40°C (10 yr)-1 in northwestern China while overestimating this quantity by 0.18°-0.33°C (10 yr)-1 in southeastern China. These trend biases in Tmax and Tmin introduce a positive trend bias in DTR of 0.01°-0.26°C (10 yr)-1 within China, especially in the north China plain and southeastern China. In the five reanalyses, owing to the sensitivity discrepancies and trend biases, the surface solar radiation Rs and precipitation frequency (PF) are notable deviation sources of the diurnal cycle of air temperature, which explain 31.0%-38.7% (31.9%-37.8%) and 9.8%-22.2% (7.4%-15.3%) of the trend bias in Tmax (DTR) over China, respectively. [ABSTRACT FROM AUTHOR]

The article discusses the study which investigates the differences and similarities of various average surface air temperature (SAT) time series in China since 1900. The study was based on the historical meteorological observations in the region that feature high-quality climate datasets wherein homogenized SAT datasets to solve discrepancies in the datasets. Result shows closed alignment between the six SAT series installed in the region.

Interdecadal variations in the relationship between the winter North Atlantic Oscillation (NAO) and surface air temperature in China are investigated using observational and reanalysis data. Focus is on south-central China, in which temperature variability is strongly related to the NAO. It is revealed that the relationship shows clear interdecadal variations in midwinter during 1951-2015. A relatively weak in-phase relationship occurs before the early 1970s (P1), but a significant out-of-phase relationship dominates in the last two decades of the twentieth century (P2), though it is clearly weaker from the late 1990s onward. Observational evidence shows that such interdecadal variations are related mainly to variations in the spatial pattern and amplitude of the NAO. The northern center of the NAO shifted eastward over the second half of the twentieth century. In addition, the amplitude of the center strengthened from P1 to P2, resulting in a perturbation in the atmospheric circulation response pattern over Eurasian mid-to-high latitudes. During P2, the eastward shift and amplitude intensification of the NAO favored a north-south dipole structure in circulation anomalies over the Asian continent, which tended to produce cold temperature anomalies in south-central China during the positive NAO phase and warm anomalies during the negative phase. However, in the past two decades the northern center of the NAO has weakened and retreated westward. This was concurrent with a weakening relationship between the NAO and temperature anomalies in south-central China and northern Eurasia, indicating weaker downstream impacts of the NAO in midwinter. [ABSTRACT FROM AUTHOR]

North China has undergone a severe drying trend since the 1950s, but whether this trend is natural variability or anthropogenic change remains unknown due to the short data length. This study extends the analysis of dry-wet changes in north China to 1900-2010 on the basis of self-calibrated Palmer drought severity index (PDSI) data. The ensemble empirical mode decomposition method is used to detect multidecadal variability. A transition from significant wetting to significant drying is detected around 1959/60. Approximately 70% of the drying trend during 1960-90 originates from 50-70-yr multidecadal variability related to Pacific decadal oscillation (PDO) phase changes. The PDSI in north China is significantly negatively correlated with the PDO index, particularly at the 50-70-yr time scale, and is also stable during 1900-2010. Composite differences between two positive PDO phases (1922-45 and 1977-2002) and one negative PDO phase (1946-76) for summer exhibit an anomalous Pacific-Japan/East Asian-Pacific patternlike teleconnection, which may develop locally in response to the PDO-associated warm sea surface temperature anomalies in the tropical Indo-Pacific Ocean and meridionally extends from the tropical western Pacific to north China along the East Asian coast. North China is dominated by an anomalous high pressure system at mid-low levels and an anticyclone at 850 hPa, which are favorable for dry conditions. In addition, a weakened land-sea thermal contrast in East Asia from a negative to a positive PDO phase also plays a role in the dry conditions in north China by weakening the East Asian summer monsoon. [ABSTRACT FROM AUTHOR]

In this study, late-summer rainfall over eastern contiguous China is classified according to hourly intensity and the changes of moderate, intense, and extreme precipitation in response to variation of surface air temperature are analyzed. The e-folding decay intensity ( Imi) derived from the exponential distribution of rainfall amount is defined as the threshold that partitions rainfall into moderate and intense rainfall, and the double e-folding decay intensity ( Ie) is used as the threshold to pick out extreme cases. The mean values of Imi and Ie are about 12 and 24 mm h−1, respectively. Between the two periods, 1966-85 and 1986-2005, the ratio between moderate and intense rainfall has experienced significant changes. And the spatial pattern of changes in the percentage of moderate rainfall presents a direct relation with that of the surface air temperature. Based on temperature changes, three regimes, regime N (north China), regime C (central eastern China), and regime S (southeastern coastal area of China), are defined. In warming regimes (regimes N and S), the percentage of moderate rainfall exhibits a decreasing trend. In regime C, where the temperature has fallen, the percentage of moderate rainfall increased prominently. In all three regimes there are significant negative (positive) correlations between the percentage of moderate (intense) rainfall and the temperature. The relation between the extreme rainfall and the surface air temperature is far more regionally dependent. With plenty of water supply and little change in relative humidity, the extreme rainfall increased in regime S. Although regime N also shows strong warming trends, there is no significant trend in extreme precipitation due to the lack of water vapor transportation. [ABSTRACT FROM AUTHOR]

Evidence is presented that the boreal summer surface air temperature over south China and northeast China is remotely influenced by the Indian Ocean Basin mode (IOBM) sea surface temperature (SST) anomalies. Above-normal temperature in south China and below-normal temperature in northeast China correspond to a simultaneous Indian Ocean Basin warming. The teleconnection from Indian Ocean SST anomalies to China summer surface air temperature is investigated using observations and an atmospheric general circulation model (AGCM). The results herein indicate that the tropical Indian Ocean Basin warming can trigger a low-level anomalous anticyclone circulation in the subtropical northwest Pacific and an anomalous cyclone circulation in midlatitude East Asia through emanating a baroclinic Kelvin wave. In south China, the reduced rainfall and downward vertical motion associated with the anomalous low-level anticyclone circulation lead to above-normal summer surface air temperature. In northeast China, by contrast, upward vertical motion associated with the anomalous cyclone leads to below-normal summer surface air temperature. [ABSTRACT FROM AUTHOR]

Annual and seasonal trends of precipitable water (PW) and relative humidity (RH) at 850, 700, and 500 hPa are studied using the data from 106 radiosonde stations over China during the period 1979-2005. Analysis shows evidence of an increase in PW associated with the slight warming observed in the lower to midtroposphere over China. The northern part of China shows a significant upward trend of PW in summer, and drying of the atmosphere in winter is found in most regions over China. Annual and seasonal trends in RH at the 850-, 700-, and 500-hPa levels show no significant trends in most regions in China except for Xinjiang, which shows an upward trend, and central China, where there was a downward trend in RH at 500 hPa. It is found that changes in PW are coincident with the warming of the surface and the lower to midtroposphere. The RH in the lower to midtroposphere in most regions over China has remained steady during the most recent 30 years, as might be expected given the increasing of PW and the warming above the surface. The long-term trend of precipitation over China may be linked to the trends of PW and RH at the lower level and midlevel. [ABSTRACT FROM AUTHOR]

Probabilistic projection of climate change consists of formulating the climate change information in a probabilistic manner at either global or regional scale. This can produce useful results for studies of the impact of climate change impact and change mitigation. In the present study, a simple yet effective approach is proposed with the purpose of producing probabilistic results of climate change over China for the middle and end of the twenty-first century under the Special Report on Emissions Scenarios A1B (SRES A1B) emission scenario. Data from 28 coupled atmosphere-ocean general circulation models (AOGCMs) are used. The methodology consists of ranking the 28 models, based on their ability to simulate climate over China in terms of two model evaluation metrics. Different weights were then given to the models according to their performances in present-day climate. Results of the evaluation for the current climate show that five models that have relatively higher resolutions-namely, the Istituto Nazionale di Geofisica e Vulcanologia ECHAM4 (INGV ECHAM4), the third climate configuration of the Met Office Unified Model (UKMO HadCM3), the CSIRO Mark version 3.5 (Mk3.5), the NCAR Community Climate System Model, version 3 (CCSM3), and the Model for Interdisciplinary Research on Climate 3.2, high-resolution version [MIROC3.2 (hires)]-perform better than others over China. Their corresponding weights (normalized to 1) are 0.289, 0.096, 0.058, 0.048, and 0.044, respectively. Under the A1B scenario, surface air temperature is projected to increase significantly for both the middle and end of the twenty-first century, with larger magnitude over the north and in winter. There are also significant increases in rainfall in the twenty-first century under the A1B scenario, especially for the period 2070-99. As far as the interannual variability is concerned, the most striking feature is that there are high probabilities for the future intensification of interannual variability of precipitation over most of China in both winter and summer. For instance, over the Yangtze-Huai River basin (28°-35°N, 105°-120°E), there is a 60%% probability of increased interannual standard deviation of precipitation by 20%% in summer, which is much higher than that of the mean precipitation. In general there are small differences between weighted and unweighted projections, but the uncertainties in the projected changes are reduced to some extent after weighting. [ABSTRACT FROM AUTHOR]

The aim of this study is to characterize the urban heat island (UHI) intensity in Hong Kong. The first objective is to explore the UHI intensity in Hong Kong by using the mobile transverse and remote sensing techniques. The second objective is to produce a satellite-derived air temperature image by integrating satellite remote sensing with a mobile survey, the methodology involved in making simultaneous ground measurements when the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) satellite made an overpass. The average UHI intensity of Hong Kong was about 2°–3.5°C, although a very high value of 12°C UHI was observed on a calm winter night by ASTER. The satellite-derived surface temperature was compared with the in situ measurements. The bias was found to be only about 1.1°C. A good correlation was also found between the in situ surface and air temperature pair of readings at nighttime on 31 January 2007. The linear regression lines of temperatures in urban and suburban areas were then used to convert the satellite-derived surface temperatures into air temperatures. The satellite-derived air temperatures showed a good correlation with temperatures observed by 12 fixed stations. It is possible to derive the nighttime air temperature from the satellite surface temperature on calm and clear winter nights. [ABSTRACT FROM AUTHOR]