Surface latent heat flux anomalies preceding inland earthquakes in China

Using data from the National Center for Environmental Prediction （NCEP）, the paper analyzed the surface latent heat flux （SLHF） variations for five inland earthquakes occurred in some lake area, moist area and arid area of China during recent years. We used the SLHF daily and monthly data to differentiate the global and seasonal variability from the transient local anomalies. The temporal scale of the observed variations is 1-2 months before and after the earthquakes, and spatial scale is about 10°×10°. The result suggests that the SLHFs adjacent the epicenters all are anomalous high value （〉μ＋2σ） 8-30 days before the shocks as compared with past several years of data. Different from the abnormal meteorological phenomenon, the distribution of the anomalies was isolated and local, which usually occurred in the epicenter and its adjacent area, or along the fault lines. The increase of SLHF was tightly related with the season which the earthquake occurs in; the maximal （125 W/m^2, Pu＇er earthquake） and minimal （25 W/m^2, Gaize earthquake） anomalies were in summer and winter, respectively. The abundant surface water and groundwater in the epicenter and its adjacent region can provide necessary condition for the change of SLHF. To further confirm the reliability of SLHF anomaly, it is necessary to explore its physical mechanism in depth by more earthquake cases.

CHARACTERISTICS OF 10-DAY MEAN SURFACE LATENT HEAT FLUX VARIATIONS IN THE SCS MONSOON REGION AND POSSIBLE CONNECTIONS WITH THE SCS SUMMER MONSOON ONSET

The temporal and spatial variations of the ten-day mean surface latent heat flux (TMLH) have been analyzed in this paper based on the data of NCEP from January of 1979 to December of 1995 in the South China Sea (SCS) monsoon region. It is found that there exist maximum centers of TMLH standard deviation in the northwest Indochina and the Indian Peninsula as well as the western Pacific, SCS, the Indian Ocean and the Bay of Bengal, and their locations and strengths change significantly during the period of SCS monsoon onset. A positive zonal deviation of TMLH occurs first in the Indochina Peninsula, apparently earlier than that in the Indian Peninsula. The appearance of maximum positive zonal deviations of TMLH approximately coincides with the summer monsoon onset. Over the Indochina and Indian Peninsulas, the TMLH increases gradually with a small amplitude of variation before the onset of summer monsoon, and the rate of increase is significantly enhanced after the onset of the monsoon; whereas over the ocean, TMLH decreases before the monsoon onset, varies little during the period of monsoon and increases gradually after the ending of monsoon. Therefore, it seems that the surface latent heat flux plays an important role in the maintenance of the summer monsoon, and its variation is an phenomenon accompanying the onset of summer monsoon.

CLIMATOLOGICAL CALCULATION OF SURFACE LATENT HEAT OVER CHINA

In the context of measurements from all the thermal balance stations over China,two methods of calculating surface latent heat for its climatic features are proposed through experiments with a range of schemes,one being the empirical type based on the relationship between ground latent heat and vapor pressure,and the other upon the Bowen ratio parameterization.Either of them has its unique merits so that they can be considered in specific case to have higher accuracy.On this basis. investigation is done of the feature of geographic distribution and annual variability of the heat across the country.

Preliminary Study on the Dynamic Variations of the Surface Thermal Flux before and after the M_S5.7 Earthquake of 2005 in Jiujiang City,Jiangxi Province

The temporal and spatial variations of surface latent heat flux(SLHF)and diagnostic air temperature at 2m before and after the M_S5.7 earthquake occurring on November 26,2005 in the area between Ruichang City and Jiujiang City,Jiangxi Province are summarized in this paper.It is found that before the earthquake significant SLHF anomalies and air temperature anomalies occurred in the epicentral area and its vicinity.The air temperature anomalies appeared from the 2nd to the 13th of November,2005 and were concentrated at the epicentral area and in its southern part.Then two days later,that is,from the 4th to the 15th of November 2005,significant SLHF anomalies occurred in the epicentral area and to its northern area where many lakes are distributed along the active faults.During the anomalous period,the SLHF and air temperature at 2m exceeded the sum of average daily value over 26 years and 1.5 times of its mean square deviation.Both anomalies had maintained for 12 days with a peculiar distribution related to the tectonic active zone.It is considered that both of air temperature anomalies and SLHF anomalies are correlated to the movement of thermal flux from underground prior to earthquake.SLHF anomalies occurred over wide regions covered with abundant water,whereas air temperature anomalies occurred over land.

Interdecadal Variability in Large and Small Warm Pools in Western Pacific and Their Association with Rainfall Anomalies

This study investigated interdecadal variability of June–October(JJASO) the large and small warm pools in western Pacific and their association with rainfall anomalies using station and reanalysis data from 1958 to 2008.The results indicated that the large and small warm pools in western Pacific showed an interdecadal shift around 1986.The large warm pool years over western Pacific were found after 1986,whereas the small warm pool years were often seen throughout the periods before 1986.The analysis results also showed that there were obvious interdecadal variability in JJASO rainfall in Southeast China and warm pool in western Pacific.During 1958–1985(small warm pool years),the decrease in rainfall was associated with tropospheric moisture divergence and sinking motion over Southeast China and warm pool in western Pacific.However,during 1986–2008(large warm pool years),the increase in rainfall was associated with tropospheric moisture convergence and ascending motion.Further analysis showed that large warm pool contributed to the increase in surface latent heat fluxes over warm pool in the western Pacific.Thus,there was an increase in the amount of water vapor over Southeast China and warm pool in western Pacific,which contributed to increased rainfall in these regions.