中国当代土地利用对区域气候影响的数值模拟

使用RegCM3区域气候模式，嵌套欧洲数值预报中心(ECMWF)ERA40再分析资料，分别进行了中国区域在实际植被和理想植被分布情况下各15年时间长度（1987-2001）的积分试验，以研究我国土地利用状况对气候的影响。通过两个试验结果的对比，研究了我国土地利用状况对气候的影响。分析主要集中于气温、降水等的变化上，并对结果进行了统计显著性检验。结果表明，当代土地利用/植被覆盖变化加强了中国地区冬、夏季的季风环流，同时改变了地表能量平衡状况，从而对各气候要素产生重要影响。冬季，植被改变引起长江以南降水减少、气温降低，长江以北降水增加。夏季，植被改变显著影响了南方地区的气候，使得这里降水增多，黄淮、江淮气温降低，华南气温上升；同时引起中国北方降水减少，气温在西北部分植被退化地区升高。植被变化对日最低、最高气温的影响更大。总体来说，土地利用引起了年平均降水在南方增加、北方减少，年平均气温在南方显著降低。     

Paleomagnetic data from tertiary igneous rocks,northeast Jalisco,Mexico

New paleomagnetic measurements have been made on Tertiary volcanic rocks from northeast Jalisco, Mexico (20.7°N, 102.3°W). The pole position obtained from this study (68°N, 181°E) is consistent with two other Oligocene poles from Mexico. Mexican poles form a coherent group which differs from poles of similar ages from North America. This suggests a possible tectonic rotation of the sampling sites of Mexico with respect to “stable” North America.     

Delineation of Rajmahal basaltic flows,inter-trappeans and associated coal layers using Audio-magneto-telluric method

The extensive volcanic activity of Rajmahal occurred during early Cretaceous (~117 Ma). Potentially perspective Gondawana sediments containing coal seam is partially covered by these basalts. Basalts as well as coal are already known to be of immense economic importance over Rajmahal traps. The present study mainly deals with delineation of basaltic lava flows and associated coal layers using the Audio-magneto-telluric (AMT) study in the south central region of Rajmahal traps near Suri, West Bengal, India. Initially, the field situations have been simulated using forward model with top alluvium cover followed by basaltic lava flows, a wedge shaped inter-trappean sedimentary formation with second basaltic lava flows and basement at the bottom. The model was constrained using available litholog. The model study reveals the presence of moderately resistive basalts, relatively conductive inter-trappeans and the basement, except the top alluvium layer and thin inter-trappeans. Subsequently, threeAMT sounding have been carried out over Cholaguria, Hatgacha and Pachami, Suri, West Bengal. The field AMT study reveals three basaltic lava flows with varying thickness from ~40m to ~350m and composite thickness of ~620m to ~640m, which match well with the published borehole litholog. The inter-trappeans have been identified at 500m to 620m, 310m to 400m and 500m to 640m depths over Cholaguria, Hatgacha and Pachami, respectively. It is interesting to mention that the identified inter-trappeans are inferred to be coal/shaly-coal which are matching very well with the published borehole lithologs.     

Calibration of a constitutive model using genetic algorithms

Before any constitutive model can be used in a numerical procedure, the model needs to be calibrated using laboratory test results. The traditional calibration techniques use stress and strain levels at certain states that a material undergoes during certain types of laboratory tests. Sometimes this method of calibrating a constitutive model fails to capture the overall behavior of a material, i.e. behavior at every point in stress/strain path. In this paper, we have shown how a random search technique, genetic algorithm (GA), can be used to calibrate constitutive models. The advantages of using GA are that it considers the overall behavior of a material, not the behavior at some specific states as the traditional method does, and it can work with many types of laboratory tests. The concept is applied to calibrate the hierarchical single surface (HiSS) δ_l model for geologic materials. Three cases have been studied where the difference is in the type of test data used to calibrate the model. These three different test data are: (1) simulated conventional test data, (2) simulated cyclic test data, and (3) real test data. A comparison of two different cross-over schemes, one-point and six-point, has been made.     

Verification of cloud cover forecast with INSAT observation over western India

Since the beginning of the summer monsoon 2009, experimental mesoscale weather forecasts in real time are being generated using WRF model by the Meteorology and Oceanography Group at the Space Applications Centre (ISRO) and are disseminated through MOSDAC () to various users. To begin with, the 12 h, 24 h and 48 h forecasts for the western India region are made available. A study is undertaken to comprehensively assess the cloudiness prediction performance of WRF model. The evaluations have been made over the three months period during monsoon 2009. INSAT cloud imagery data has been used as a reference for these evaluations. The verification strategy includes computation of various skill scores. It is seen that probability of detection (POD) of cloud is 84% and the false alarm rate (FAR) is around 18%. It is hoped that this assessment will provide information on the use of these forecasts in various applications.     

Accuracy improvement of ASTER stereo satellite generated DEM using texture filter

The grid DEM(digital elevation model) generation can be from any of a number of sources:for instance,analogue to digital conversion of contour maps followed by application of the TIN model,or direct elevation point modelling via digital photogrammetry applied to airborne images or satellite images.Currently,apart from the deployment of point-clouds from LiDAR data acquisition,the generally favoured approach refers to applications of digital photogrammetry.One of the most important steps in such deployment i...