WetNet: Using SSM/I data interactively for global distribution of tropical rainfall and precipitable water

The research objectives were the following: (1) to use SSM/I to categorize, measure, and parameterize effects of rainfall systems around the globe, especially mesoscale convective systems; (2) to use SSM/I to monitor key components of the global hydrologic cycle, including tropical rainfall and precipitable water, and links to increasing sea surface temperatures; and (3) to assist in the development of efficient methods of exchange of massive satellite data bases and of analysis techniques, especially their use at a university. Numerous tasks have been initiated. First and foremost has been the integration and startup of the WetNet computer system into the TAMU computer network. Scientific activity was infeasible before completion of this activity. Final hardware delivery was not completed until October 1991, after which followed a period of identification and solution of several hardware and software and software problems. Accomplishments representing approximately four months work with the WetNEt system are presented

WetNet: Using SSM/I data interactively for global distribution of rainfall and precipitable water

By completing hardware installation, preparing for comparative studies of SSM/I, radar, and lightning data, it is believed that this will be a powerful combination for evaluating the global distribution of tropical rainfall, and the vertical distribution of latent heating, with strong application to algorithms for use on TRMM, EOS-A, and future GOES spacecraft. Potential data bases will be surveyed, about 5 case studies with surface rainfall, radar, lightning, and sounding data will be identified. SSM/I algorithms will be used to identify convective regions of MCSs. A catalog will be developed of the global profile of heavy tropical rainfall, and how these zones are organized within larger tropical weather systems. Beginning with the first few months of SSM/I data distributed over WetNet, SSM/I radiances will be compared with TOVS radiance (moisture and thermal) and OLR observations. The purpose is to improve understanding of how real world water vapor profiles in the tropical atmosphere are perceived by SSM/I precipitable water algorithm and, at the same time, by the TOVS water vapor channel

A regional climatology of monsoonal precipitation in the southwestern United States using TRMM

ABSTRACT Using 13 yr of data from the Tropical Rainfall Measuring Mission (TRMM) satellite, a regional climatology of monsoonal precipitation is created for portions of the southwest United States. The climatology created using precipitation features defined from the TRMM precipitation radar (PR) shows that the population of features includes a large number of small, weak features that do not produce much rain and are very shallow. A lesser percentage of large, stronger features contributes most of the region's rainfall. Dividing the features into categories based on the median values of volumetric rainfall and maximum height of the 30-dBZ echo is a useful way to visualize the population of features, and the categories selected reflect the life cycle of monsoonal convection. An examination of the top rain-producing features at different elevations reveals that extreme features tend to occur at lower elevations later in the day. A comparison with the region studied in the North American Monsoon Experiment (NAME) shows that similar diurnal patterns occur in the Sierra Madre Occidental region of Mexico. The population of precipitation features in both regions is similar, with the NAME region producing slightly larger precipitation systems on average than the southwest United States. Both regions on occasion demonstrate the pattern of convection initiating at high elevations and moving downslope while growing upscale through the afternoon and evening; however, there are also days on which convection remains over the high terrain

Diurnal Variations of Global Thunderstorms and Electrified Shower Clouds and Their Contribution to the Global Electrical Circuit

ABSTRACT The long-standing mainstay of support for C. T. R. Wilson's global circuit hypothesis is the similarity between the diurnal variation of thunderstorm days in universal time and the Carnegie curve of electrical potential gradient. This rough agreement has sustained the widespread view that thunderstorms are the ''batteries'' for the global electrical circuit. This study utilizes 10 years of Tropical Rainfall Measuring Mission (TRMM) observations to quantify the global occurrence of thunderstorms with much better accuracy and to validate the comparison by F. J. W. Whipple 80 years ago. The results support Wilson's original ideas that both thunderstorms and electrified shower clouds contribute to the DC global circuit by virtue of negative charge carried downward by precipitation. First, the precipitation features (PFs) are defined by grouping the pixels with rain using 10 years of TRMM observations. Thunderstorms are identified from these PFs with lightning flashes observed by the Lightning Imaging Sensor. PFs without lightning flashes but with a 30-dBZ radar echotop temperature lower than 2108C over land and 2178C over ocean are selected as possibly electrified shower clouds. The universal diurnal variation of rainfall, the raining area from the thunderstorms, and possibly electrified shower clouds in different seasons are derived and compared with the diurnal variations of the electric field observed at Vostok, Antarctica. The result shows a substantially better match from the updated diurnal variations of the thunderstorm area to the Carnegie curve than Whipple showed. However, to fully understand and quantify the amount of negative charge carried downward by precipitation in electrified storms, more observations of precipitation current in different types of electrified shower clouds are required

Legacy of Precipitation Feature Database from Satellite Passive Microwave Radiometer and Precipitation Radar Observations

No abstract availabl

Three years of TRMM precipitation features. Part I: Radar, radiometric, and lightning characteristics,

ABSTRACT During its first three years, the Tropical Rainfall Measuring Mission (TRMM) satellite observed nearly six million precipitation features. The population of precipitation features is sorted by lightning flash rate, minimum brightness temperature, maximum radar reflectivity, areal extent, and volumetric rainfall. For each of these characteristics, essentially describing the convective intensity or the size of the features, the population is broken into categories consisting of the top 0.001%, top 0.01%, top 0.1%, top 1%, top 2.4%, and remaining 97.6%. The set of "weakest/smallest" features composes 97.6% of the population because that fraction does not have detected lightning, with a minimum detectable flash rate of 0.7 flashes (fl) min Ϫ1 . The greatest observed flash rate is 1351 fl min Ϫ1 ; the lowest brightness temperatures are 42 K (85 GHz) and 69 K (37 GHz). The largest precipitation feature covers 335 000 km 2 , and the greatest rainfall from an individual precipitation feature exceeds 2 ϫ 10 12 kg h Ϫ1 of water. There is considerable overlap between the greatest storms according to different measures of convective intensity. The largest storms are mostly independent of the most intense storms. The set of storms producing the most rainfall is a convolution of the largest and the most intense storms. This analysis is a composite of the global Tropics and subtropics. Significant variability is known to exist between locations, seasons, and meteorological regimes. Such variability will be examined in Part II. In Part I, only a crude land-ocean separation is made. The known differences in bulk lightning flash rates over land and ocean result from at least two differences in the precipitation feature population: the frequency of occurrence of intense storms and the magnitude of those intense storms that do occur. Even when restricted to storms with the same brightness temperature, same size, or same radar reflectivity aloft, the storms over water are considerably less likely to produce lightning than are comparable storms over land

Weather Avoidance Guidelines for NASA Global Hawk High-Altitude Unmanned Aircraft Systems (UAS)

The current Global Hawk flight rules would probably not have been effective in the single event of greatest concern (the Emily encounter). The cloud top had not reached 50,000 ft until minutes before the encounter. The TOT and lightning data would not have been available until near the overflight time since this was a rapidly growing cell. This case would have required a lastminute diversion when lightning became frequent. Avoiding such a cell probably requires continual monitoring of the forward camera and storm scope, whether or not cloud tops have been exceeding specific limits. However, the current overflight rules as strictly interpreted would have prohibited significant fractions of the successful Global Hawk overpasses of Karl and Matthew that proved not to be hazardous. Many other high altitude aircraft (ER2 and Global Hawk) flights in NASA tropical cyclone field programs have successfully overflown deep convective clouds without incident.The convective cell that caused serious concern about the safety of the ER2 in Emily was especially strong for a tropical cyclone environment, probably as strong or stronger than any that was overflown by the ER2 in 20 previous flights over tropical cyclones. Specifically, what made that cell a safety concern was the magnitude of the vertical velocity of the updraft, at least 20 m/s (4000 ft/minute) at the time the ER2 overflew it. Such a strong updraft can generate strong gravity waves at and above the tropopause, posing a potential danger to aircraft far above the maximum altitude of the updraft itself or its associated cloud top. Indeed, the ER2 was probably at least 9000 ft above that cloud top. Cloudtop height, by itself, is not an especially good indicator of the intensity of convection and the likelihood of turbulence. Nor is overflying high cloud tops (i.e. > 50,000 ft) of particular concern unless there is other evidence of very strong convective updrafts beneath those tops in the path of the aircraft. center dot Lightning, especially lightning with a high flash rate, is well correlated with convective intensity. Lightning with a minimal flash rate (say 13 flashes per minute) is indicative of updraft speeds of about 10 m/s in the mixed phase region where charge is being separated, generally at altitudes about 2025 kft in a hurricane. That is still stronger than typical updrafts (more like 5 m/s). An unresolved issue is whether there is a high and instantaneous correlation between vertical velocity in the middle troposphere (necessary for lightning generation) and near cloud top (more direct concern for overflights)

The Saharan Air Layer and the Fate of African Easterly Waves—NASA's AMMA Field Study of Tropical Cyclogenesis

In 2006, NASA led a field campaign to investigate the factors that control the fate of African easterly waves (AEWs) moving westward into the tropical Atlantic Ocean. Aircraft and surface-based equipment were based on Cape Verde's islands, helping to fill some of the data void between Africa and the Caribbean. Taking advantage of the international African Monsoon Multidisciplinary Analysis (AMMA) program over the continent, the NASA–AMMA (NAMMA) program used enhanced upstream data, whereas NOAA aircraft farther west in the Atlantic studied several of the storms downstream. Seven AEWs were studied during AMMA, with at least two becoming tropical cyclones. Some of the waves that did not develop while being sampled near Cape Verde likely intensified in the central Atlantic instead. NAMMA observations were able to distinguish between the large-scale wave structure and the smaller-scale vorticity maxima that often form within the waves. A special complication of the east Atlantic environment is the Saharan air layer (SAL), which frequently accompanies the AEWs and may introduce dry air and heavy aerosol loading into the convective storm systems in the AEWs. One of the main achievements of NAMMA was the acquisition of a database of remote sensing and in situ observations of the properties of the SAL, enabling dynamic models and satellite retrieval algorithms to be evaluated against high-quality real data. Ongoing research with this database will help determine how the SAL influences cloud micro-physics and perhaps also tropical cyclogenesis, as well as the more general question of recognizing the properties of small-scale vorticity maxima within tropical waves that are more likely to become tropical cyclones

Multiplicity of cerebrospinal fluid functions: New challenges in health and disease

This review integrates eight aspects of cerebrospinal fluid (CSF) circulatory dynamics: formation rate, pressure, flow, volume, turnover rate, composition, recycling and reabsorption. Novel ways to modulate CSF formation emanate from recent analyses of choroid plexus transcription factors (E2F5), ion transporters (NaHCO3 cotransport), transport enzymes (isoforms of carbonic anhydrase), aquaporin 1 regulation, and plasticity of receptors for fluid-regulating neuropeptides. A greater appreciation of CSF pressure (CSFP) is being generated by fresh insights on peptidergic regulatory servomechanisms, the role of dysfunctional ependyma and circumventricular organs in causing congenital hydrocephalus, and the clinical use of algorithms to delineate CSFP waveforms for diagnostic and prognostic utility. Increasing attention focuses on CSF flow: how it impacts cerebral metabolism and hemodynamics, neural stem cell progression in the subventricular zone, and catabolite/peptide clearance from the CNS. The pathophysiological significance of changes in CSF volume is assessed from the respective viewpoints of hemodynamics (choroid plexus blood flow and pulsatility), hydrodynamics (choroidal hypo- and hypersecretion) and neuroendocrine factors (i.e., coordinated regulation by atrial natriuretic peptide, arginine vasopressin and basic fibroblast growth factor). In aging, normal pressure hydrocephalus and Alzheimer's disease, the expanding CSF space reduces the CSF turnover rate, thus compromising the CSF sink action to clear harmful metabolites (e.g., amyloid) from the CNS. Dwindling CSF dynamics greatly harms the interstitial environment of neurons. Accordingly the altered CSF composition in neurodegenerative diseases and senescence, because of adverse effects on neural processes and cognition, needs more effective clinical management. CSF recycling between subarachnoid space, brain and ventricles promotes interstitial fluid (ISF) convection with both trophic and excretory benefits. Finally, CSF reabsorption via multiple pathways (olfactory and spinal arachnoidal bulk flow) is likely complemented by fluid clearance across capillary walls (aquaporin 4) and arachnoid villi when CSFP and fluid retention are markedly elevated. A model is presented that links CSF and ISF homeostasis to coordinated fluxes of water and solutes at both the blood-CSF and blood-brain transport interfaces

Connecting the Properties of Anvil Cirrus to the Properties of the Convective Source

This final grant report describes program in preparation for and participation in the CRYSTAL-FACE Field Program, results for a master's thesis, CRYSTAL-FACE Florida case studies, and using CRMS to relate convective intensity to cirrus properties