Tropical cyclone intensity estimation is a challenging task as it required domain knowledge while extracting features, significant pre-processing, various sets of parameters obtained from satellites, ...and human intervention for analysis. The inconsistency of results, significant pre-processing of data, complexity of the problem domain, and problems on generalizability are some of the issues related to intensity estimation. In this study, we design a deep convolutional neural network architecture for categorizing hurricanes based on intensity using graphics processing unit. Our model has achieved better accuracy and lower root-mean-square error by just using satellite images than 'state-of-the-art' techniques. Visualizations of learned features at various layers and their deconvolutions are also presented for understanding the learning process.
An 8-yr climatology of storms producing large hail is estimated from satellite measurements using Advanced Microwave Scanning Radiometer for Earth Observing System (AMSR-E). This allows a unique, ...consistent comparison between regions that cannot be consistently compared using ground-based records because of varying data collection standards. Severe hailstorms are indicated most often in a broad region of northern Argentina and southern Paraguay and a smaller region in Bangladesh and eastern India. Numerous hailstorms are also estimated in the central and southeastern United States, northern Pakistan and north-western India, central and western Africa, and southeastern Africa (and adjacent waters). Fewer hailstorms are estimated for other regions over land and scattered across subtropical oceans. Very few are estimated in the deep tropics other than in Africa. Most continental regions show seasonality with hailstorms peaking in late spring or summer. The South Asian monsoon alters the hailstorm climatology around the Indian subcontinent. About 75% of the hailstorms on the eastern side (around Bangladesh) occur from April through June, generally before monsoon onset. Activity shifts northwest to northern India in late June and July. An arc along the foothills in northern Pakistan becomes particularly active from mid-June through mid-August. The AMSR-E measurements are limited to early afternoon and late night. Tropical Rainfall Measuring Mission (TRMM) measurements are used to investigate diurnal variability in the tropics and subtropics. All of the prominent regions have hailstorm peaks in late afternoon and early evening. The United States and central Africa have the fewest overnight and early morning storms, while subtropical South America and Bangladesh have the most.
Gridded climatologies of total lightning flash rates observed by the spaceborne Optical Transient Detector (OTD) and Lightning Imaging Sensor (LIS) instruments have been updated. OTD collected data ...from May 1995 to March 2000. LIS data (equatorward of about 38 degree ) adds the years 1998-2010. Flash counts from each instrument are scaled by the best available estimates of detection efficiency. The long LIS record makes the merged climatology most robust in the tropics and subtropics, while the high latitude data is entirely from OTD. The gridded climatologies include annual mean flash rate on a 0.5 degree grid, mean diurnal cycle of flash rate on a 2.5 degree grid with 24hour resolution, mean annual cycle of flash rate on a 0.5 degree or 2.5 degree grid with daily, monthly, or seasonal resolution, mean annual cycle of the diurnal cycle on a 2.5 degree grid with two hour resolution for each day, and time series of flash rate over the sixteen year record with roughly three-month smoothing. For some of these (e.g., annual cycle of the diurnal cycle), more smoothing is necessary for results to be robust. The mean global flash rate from the merged climatology is 46flashess-1. This varies from around 35flashess-1 in February (austral summer) to 60flashess-1 in August (boreal summer). The peak annual flash rate at 0.5 degree scale is 160flkm-2 yr-1 in eastern Congo. The peak monthly average flash rate at 2.5 degree scale is 18flkm-2 mo-1 from early April to early May in the Brahmaputra Valley of far eastern India. Lightning decreases in this region during the monsoon season, but increases further north and west. An August peak in northern Pakistan also exceeds any monthly averages from Africa, despite central Africa having the greatest yearly average.
Coefficients are derived for computing the polarization-corrected temperature (PCT) for 10-, 19-, 37- and 89-GHz (and similar) frequencies, with applicability to satellites in the Global ...Precipitation Measurement mission constellation and their predecessors. PCTs for 10- and 19-GHz frequencies have been nonexistent or seldom used in the past; developing those is the main goal of this study. For 37 and 89 GHz, other formulations of PCT have already become well established. We consider those frequencies here in order to test whether the large sample sizes that are readily available now would point to different formulations of PCT. The purpose of the PCT is to reduce the effects of surface emissivity differences in a scene and draw attention to ice scattering signals related to precipitation. In particular, our intention is to develop a PCT formula that minimizes the differences between land and water surfaces, so that signatures resulting from deep convection are not easily confused with water surfaces. The new formulations of PCT for 10- and 19-GHz measurements hold promise for identifying and investigating intense convection. Four examples are shown from relevant cases. The PCT for each frequency is effective at drawing attention to the most intense convection, and removing ambiguous signals that are related to underlying land or water surfaces. For 37 and 89 GHz, the older formulations of PCT from the literature yield generally similar values as ours, with the differences mainly being a few kelvins over oceans. An optimal formulation of PCT can depend on location and season; results are presented here separated by latitude and month.
PAD4 has been strongly implicated in the pathogenesis of autoimmune, cardiovascular and oncological diseases through clinical genetics and gene disruption in mice. New selective PAD4 inhibitors ...binding a calcium-deficient form of the PAD4 enzyme have validated the critical enzymatic role of human and mouse PAD4 in both histone citrullination and neutrophil extracellular trap formation for, to our knowledge, the first time. The therapeutic potential of PAD4 inhibitors can now be explored.
Large hail is a primary contributor to damages and loss around the world, in both agriculture and infrastructure. The sensitivity of passive microwave radiometer measurements to scattering by hail ...led to the development of proxies for severe hail, most of which use brightness temperature thresholds from 37-GHz and higher-frequency microwave channels on board weather satellites in low-Earth orbit. Using 16+ years of data from the Tropical Rainfall Measuring Mission (TRMM; 36°S–36°N), we pair TRMM brightness temperature–derived precipitation features with surface hail reports in the United States to train a hail retrieval on passive microwave data from the 10-, 19-, 37-, and 85-GHz channels based on probability curves fit to the microwave data. We then apply this hail retrieval to features in the Global Precipitation Measurement (GPM) domain (from 69°S to 69°N) to develop a nearly global passive microwave–based climatology of hail. The extended domain of the GPM satellite into higher latitudes requires filtering out features that we believe are over icy and snowy surface regimes. We also normalize brightness temperature depression by tropopause height in an effort to account for differences in storm depth between the tropics and higher latitudes. Our results show the highest hail frequencies in the region of northern Argentina through Paraguay, Uruguay, and southern Brazil; the central United States; and a swath of Africa just south of the Sahel. Smaller hot spots include Pakistan, eastern India, and Bangladesh. A notable difference between these results and many prior satellite-based studies is that central Africa, while still active in our climatology, does not rival the aforementioned regions in retrieved hailstorm frequency.
An event-based method of analyzing the measurements from multiple satellite sensors is presented by using observations of the Tropical Rainfall Measuring Mission (TRMM) precipitation radar (PR), ...Microwave Imager (TMI), Visible and Infrared Scanner (VIRS), and Lightning Imaging System (LIS). First, the observations from PR, VIRS, TMI, and LIS are temporally and spatially collocated. Then the cloud and precipitation features are defined by grouping contiguous pixels using various criteria, including surface rain, cold infrared, or microwave brightness temperature. The characteristics of measurements from different sensors inside these features are summarized. Then, climatological descriptions of many properties of the identified features are generated. This analysis method condenses the original information of pixel-level measurements into the properties of events, which can greatly increase the efficiency of searching and sorting the observed historical events. Using the TRMM cloud and precipitation feature database, the regional variations of rainfall contribution by features with different size, intensity, and PR reflectivity vertical structure are shown. Above the freezing level, land storms tend to have larger 20-dBZarea and reach higher altitude than is the case for oceanic storms, especially those land storms over central Africa. Horizontal size and the maximum reflectivity of oceanic storms decrease with altitude. For land storms, these intensity measures increase with altitude between 2 km and the freezing level and decrease more slowly with altitude above the freezing level than for ocean storms.
Relationships between the vertical profile of radar reflectivity and lightning flash rates are investigated using 13 years of Tropical Rainfall Measuring Mission (TRMM) observations during 1998–2010. ...First the Radar Precipitation Features (RPFs) are defined by grouping raining areas detected by the TRMM Precipitation Radar (PR). Then the characteristics of radar reflectivity and lightning flash rate are calculated in each RPF using PR and Lightning Imaging Sensor (LIS) observations. Using these RPFs, temperatures at 20, 30, and 40 dBZ radar echo tops, used as proxies of the maximum convective intensity of precipitation systems, are examined as indicators of the probability of lightning. Although 30 and 40 dBZ echo top temperatures are better indicators of the probability of lightning than the 20 dBZ echo top temperature, there is a large regional variation in the temperature thresholds, especially between land and ocean. In general, oceanic thunderstorms have higher 20 dBZ echo top and larger horizontal extent than those over land. However, radar reflectivity is more likely to exceed 30 and 40 dBZ at cold temperatures over land than over ocean. The correlations between flash rates and radar echo top temperatures, areas and volumes of radar reflectivity, and ice water contents in the mixed phase region are analyzed using RPFs with at least one flash. In agreement with previous studies, the correlations with the echo top temperatures are low, but the correlations between flash rates and areas and volumes of high radar reflectivity in the mixed phase region are much higher. There is a high correlation between the flash rates and the volumes with radar reflectivity greater than 30, 35, or 40 dBZ in the mixed phase region, but the correlation coefficient varies significantly between thunderstorms over different regions, especially between land and ocean. These results are confirmed by repeating the analysis for regions of the storms defined as convective, thus eliminating the contribution from large areas of stratiform radar echo that have much less lightning.
Key Points
Best relationships are found between lightning rate and radar reflectivity
A large regional variations of the relationships
Amazon has same radar reflectivity as ocean, but has more lightning
The Lightning Imaging Sensor (LIS) on the Tropical Rainfall Measuring Mission (TRMM) satellite has previously been used to build climatologies of mean lightning flash rate across the global tropics ...and subtropics. This new work explores climatologies of thunderstorm occurrence as seen by LIS and the conditional mean flash rates when thunderstorms do occur. The region where thunderstorms are seen most often by LIS extends slightly farther east in central Africa than the corresponding region with the highest total mean annual flash rates. Presumably this reflects a difference between more frequent thunderstorm initiation in the east and upscale growth as storms move westward. There are some differences between locations with the greatest total lightning flash counts and those where thunderstorms occur most often. The greatest conditional mean flash rates—considering only those TRMM orbits that do have lightning in a given grid box—are found in subtropical regions. The highest values are in Argentina, with the central United States, Pakistan, eastern China, and the east coast of Australia also having particularly high values.
The Tropical Rainfall Measuring Mission (TRMM) satellite has been used to infer distributions of intense thunderstorms. Besides the lightning measurements from TRMM, the radar reflectivities and ...passive microwave brightness temperatures have been used as proxies for convective vigor. This is based on large graupel or hail lofted by strong updrafts being the cause of high–radar reflectivity values aloft and extremely low brightness temperatures. This paper seeks to empirically confirm that extremely low brightness temperatures are often accompanied by large hail at the surface. The three frequencies examined (85, 37, and 19GHz) all show an increasing likelihood of hail reports with decreasing brightness temperature. Quantification is limited by the sparsity of hail reports. Hail reports are common when brightness temperatures are below 70 K at 85 GHz, 180 K at 37 GHz, or 230 K at 19 GHz.
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