Spatial variability of surface rainfall as observed from TRMM field campaign data

The spatial variability of surface rainfall over 5- and 30-day time periods is observed, and it is found that the spatial decorrelation length of precipitation is comparable to the size of a single surface gauge network. The observed variability is found to affect radar-derived precipitation estimation, particularly if it is based on calibration using rain gauges. The radar subgrid-scale variability is also observed using some redundant and finer-scale gauge networks deployed during the Tropical Rainfall Measuring Mission ( TRMM) ground-validation field campaigns. Based upon statistical analysis and a point-based decision-making system, a best-suited spatial temporal filtering technique is suggested and, when applied to match radar data with any other surface observation, is found to reduce bias

Supervised learning applied to high-dimensional millimeter wave transient absorption data for age prediction of perovskite thin-film

We have analyzed a limited sample set of 120 GHz, and 150 GHz time-resolved millimeter wave (mmW) photoconductive decay (mmPCD) signals of 300 nm thick air-stable encapsulated perovskite film (methyl-ammonium lead halide) excited using a pulsed 532-nm laser with fluence 10.6 micro-Joules per cm-2. We correlated 12 parameters derived directly from acquired mmPCD kinetic-trace data and its step-response, each with the sample-age based on the date of the experiment. Five parameters with a high negative correlation with sample age were finally selected as predictors in the Gaussian Process Regression (GPR) machine learning model for prediction of the age of the sample. The effects of aging (between 0 and 40,000 hours after film production) are quantified mainly in terms of a shift in peak voltage, the response ratio (conductance parameter), loss-compensated transmission coefficient, and the radiofrequency (RF) area of the transient itself (flux). Changes in the other step-response parameters and the decay length of the aging transients are also shown. The GPR model is found to work well for a forward prediction of the age of the sample using this method. It is noted that the Matern-5 over 2 GPR kernel for supervised learning provides the best realistic solution for age prediction with R squared around 0.97

Evaluation Of Trmm Precipitation Radar Rainfall Estimates Using Nexrad And Rain Gauges In Central And South Florida

Monthly rate accumulation on 0.5° × 0.5° Lat/Lon boxes was estimated using Next Generation Radar WSR-88D (NEXRAD) and using rain gauges for the central Florida region during Texas/Florida Underflights Experiment (TEFLUN-B). The NEXRAD derived accumulation was within 45 mm rms of the individual boxes for a box average accumulation of 167 mm. For purposes of comparison, estimates of monthly average rain rate, on the same boxes, were made using NEXRAD and PR for both central and south Florida regions during the same period. It was found that the PR RainAllMean rain rate product does yield a reasonable estimate that is about a factor of 2 too high compared with the corresponding NEXRAD estimates. Comparisons with the PR RainMean product showed that they differ by a factor of 4 (PR greater than NEXRAD)

Coupling of the finite-difference method and the boundary element - dual reciprocity method for wind flow simulation

This paper discusses an on-going research effort to develop a more computationally efficient scheme, for the direct simulation of wind flow around bluff bodies. Direct simulation as used in this study is based on providing a robust numerical solution to the 2-D primitive variable form of the Navier-Stokes equations. This approach to simulation of wind flow is increasingly becoming more attractive, especially, since very fast and low-cost computers are now readily available to most users. The objective of the present study is thus, to enhance the computational speed of an existing finite-difference-based wind simulation scheme already implemented by the authors. The resulting wind flow simulation software is designed for use in an engineering workstation environment, in which, the new coupled scheme offers more efficient and improved computational effort. The main thrust of this paper is a discussion of the mathematical modeling of the new coupled scheme, and finally a presentation of some preliminary results obtained from numerical experimentation

Environmental Characteristics of Convective Systems During TRMM-LBA

In this paper, data collected from 51 days of continual upper atmospheric soundings and TOGA radar at ABRACOS Hill during the TRMM-LBA experiment are used to describe the mean thermodynamic and kinematic airmass properties of wet season convection over Rondonia, Brazil. Distinct multi-day easterly and westerly lower tropospheric wind regimes occurred during the campaign with contrasting airmass characteristics. Westerly wind periods featured modest CAPE (1000 J/kg), moist conditions (>90% RH) extending through 700 mb and shallow (900 mb) speed shear on the order of 10(exp -4)/s. This combination of characteristics promoted convective systems that featured a relatively large fraction of stratiform rainfall and weak convection nearly devoid of lightning. The environment is very similar to the general airmass conditions experienced during the Darwin, Australia monsoon convective regime. In contrast, easterly regime convective systems were more strongly electrified and featured larger convective rain rates and reduced stratiform rainfall fraction. These systems formed in an environment with significantly larger CAPE (1500 J/kg), drier lower and middle level humidities (< 80% RH) and a wind shear layer that was both stronger (10(exp -3)/s) and deeper (700 mb). The larger CAPE resulted from strong insolation under relatively cloud-free skies (owing to reduced column humidity) and was also weakly capped in the lowest 1-2 km, thus contributing to a more explosive growth of convection. The time series of low- and mid-level averaged humidity exhibited marked variability between westerly and easterly regimes and was characterized by low frequency (i.e., multi-day to weekly) oscillations. The synoptic scale origins of these moisture fluctuations are examined, which include the effects of variable low-level airmass trajectories and upper-level, westward migrating cyclonic vortices. The results reported herein provide an environmental context for ongoing dual Doppler analyses and numerical modeling case studies of individual TRMM-LBA convective systems