混合同化方法同化地面站和雷达观测对飑线影响的模拟观测试验

利用中尺度天气预报模式和混合同化方法ETKF-3DVAR进行模拟观测试验,对比同化地面站观测数据和雷达观测结果对改善中国东部一次飑线模拟的影响.结果表明,无论是采用混合同化方法还是3DVAR,同化地面站观测均能改善分析场和预报场;若再增加同化雷达观测,结果还会进一步改善,其中混合方法对低层要素场和累计降水量的改进更大.

Contrast patterns and trends of lapse rates calculated from near-surface air and land surface temperatures in China from 1961 to 2014

The near-surface lapse rate reflects the atmospheric stability above the surface.Lapse rates calculated from land surface temperature(γTs)and near-surface air temperature( γTa )have been widely used.However,γTs and γTa have different sensitivity to local surface energy balance and large-scale energy transport and therefore they may have diverse spatial and temporal variability,which has not been clearly illustrated in existing studies.In this study,we calculated and compared γTa and γTs at^2200 stations over China from 1961 to 2014.This study finds that γTa and γTs have a similar multiyear national average(0.53°C/100 m)and seasonal cycle.Nevertheless,γTs shows steeper multiyear average than γTa at high latitudes,and γTs in summer is steeper than γTa ,especially in Northwest China.The North China shows the shallowest γTa and γTs,then inhibiting the vertical diffusion of air pollutants and further reducing the lapse rates due to accumulation of pollutants.Moreover,the long-term trend signs for γTa and γTs are opposite in northern China.However,the trends in γTa and γTs are both negative in Southwest China and positive in Southeast China.Surface incident solar radiation,surface downward longwave radiation and precipitant frequency jointly can account for 80%and 75%of the long-term trends in γTa and γTs in China,respectively,which provides an explanation of trends of γTa and γTs from perspective of surface energy balance.

A terrestrial observatory approach to the integrated investigation of the effects of deforestation on water,energy,and matter fluxes

Integrated observation platforms have been set up to investigate consequences of global change within a terrestrial network of observatories （TERENO） in Germany. The aim of TERENO is to foster the understanding of water, energy, and matter fluxes in terrestrial systems, as well as their biological and physical drivers. Part of the Lower Rhine Valley-Eifel observatory of TERENO is located within the Eifel National Park. Recently, the National Park forest management started to promote the nat- ural regeneration of near-natural beech forest by removing a significant proportion of the spruce forest that was established for timber production after World War II. Within this context, the effects of such a disturbance on forest ecosystem functioning are currently investigated in a deforestation experiment in the Wtistebach catchment, which is one of the key experimental re- search sites within the Lower Rhine Valley-Eifel observatory. Here, we present the integrated observation system of the Wiistebach test site to exemplarily demonstrate the terrestrial observatory concept of TERENO that allows for a detailed mon- itoring of changes in hydrological and biogeochemical states and fluxes triggered by environmental disturbances. We present the observation platforms and the soil sampling campaign, as well as preliminary results including an analysis of data con- sistency. We specifically highlight the capability of integrated datasets to enable improved process understanding of the post-deforestation changes in ecosystem functioning.

Comparison of long-term total ozone observations from space-and ground-based methods at Zhongshan Station,Antarctica

Total ozone errors for satellite observations at Zhongshan Station in Antarctica are characterized using their relative difference （RD） from ground-based Brewer observations during 1993-2015. All satellite total ozone observations slightly overestimated ground-based ones （with RD less than 4%）. This is in contrast to conclusions drawn from global-scale validation studies, where main ground-based reference stations are located in middle latitudes. Given multiple total ozone data per day at Zhongshan Station, observed by a sun synchronous orbit satellite, measurements at the lowest solar zenith angle （SZA） show greatest consistency with Brewer ones, having an overall RD of-0.02-1.15%. Algorithm-retrieved total ozone data from the Total Ozone Mapping Spectrometer （TOMS）, including Solar Backscatter Ultra Violet （SBUV）, TOMS-Earth Probe （EP）, Ozone Monitoring Instrument （OMI）-TOMS, show best agreement with ground-based values; followed by the Global Ozone Measurement Experiment-type Direct Fitting （GOD-FIT） algorithm for the GOME-2A, and finally the Differential Optical Absorption Spectroscopy （DOAS） --Algorithm retrieved products for satellites-detectors of Global Ozone Measurement Experiment （GOME）, Scanning Imaging Absorption spectroMetr for Atmospheric CHartographY （SCIAMACHY）, and OMI. Satellite total ozone RD presents some statistical characteristics, but no specific trends. DOAS and GOME-2A algorithms have values that significantly increase, when the SZA is above 60°-70°, whereas values for GOME-2A decrease, when the SZA is 80-85°. Satellite total ozone RD is a minimum, when the Brewer total ozone is 300-350 DU, with an obvious increase in RD values for DOAS- and GOME-2A, when the Brewer total ozone is 150-300 DU. Satellite total ozone RD obviously increases, as the time difference between satellite overpasses and Brewer measurements grows. Specifically, RD rises as the absolute time difference increases to more than 4 h, yielding an OMI-TOMS RD of more than 10% as this difference increases to 8 h. The DOAS- RD may be up to 15%, while GOME-2A RD does not exceed 10%. The satellite total ozone RD may reach -5%, as the distance between the satellite overpass pixel and the station become more than 100 km. Possibly because of the discrepancy in surface albedo, the TOMS-algorithm retrieved total ozone produced underestimation, when the pixel on the south-east side of the station （the Antarctica continent） is used, but overestimation on the north-west side of the station （the Indian Ocean）. Consistency between space and ground-based total ozone data is least for the ＂ozone hole＂. Typically, the RD of TOMS-algorittun retrieved total ozone is within 1%/10 yr. Thus, the SBUV and Brewer monthly averaged total ozone anomalies from 1996 to 2015 were 1%/10 yr and 0.9%/10 yr, respectively. Both indicate slight, but consistent, ozone layer recovery.