nasa-gesdisc/es-publications-researchareas huggingface dataset:
Characteristics of deep convective clouds, precipitation, and cloud properties of rapidly intensifying tropical cyclones in the western North Pacific (2022)

Toward the understanding of rapid intensification (RI) of tropical cyclones (TCs) in the western North Pacific, the TC's deep convective cloud (DCC), precipitation, and cloud properties in terms of cloud effective radius, optical thickness, and top height from satellite observations are investigated. Mean and radial distributions of the variables at different intensity stages and intensification categories are examined. The relationship indicates that the DCC percentage and temperature, especially their radial distributions, could be used to identify an impending RI regardless of TC intensity. Meanwhile, the mean and radial distribution of precipitation may discriminate RI from non-RI in tropical depression (TD) and tropical storm (TS). The radial distribution of the cloud properties in rapidly intensifying TD and TS also suggest that most of the clouds near the center of the storm has deepened already while those that are far from the center are generally in developing or dissipating stage. Moreover, rapidly intensifying TCs, regardless of their intensities, manifest common DCC, precipitation, and cloud properties characteristics near the TC center. It is to be noted that the different mean and radial distribution characteristics of the variables between initial and continuing stages of RI are inferred to be artifacts of their intensities and RI rates (or radius of maximum wind sizes) rather than whether the TCs are at the onset or 24 hr of RI.

Research areas: Severe Storms
Upright Convection in Extratropical Cyclones: A Survey Using (2020)

Upright convection can impact extratropical cyclone (ETC) precipitation and dynamics differently than isentropic ascent, but how often it occurs and how much it contributes to total precipitation within an ETC have not been systematically documented in previous literature. Herein, convection in ETCs is analyzed using ground-based radar observations over the Eastern United States. Convection occupies 1%-5% of the precipitating region and constitutes 1%-15% of total cyclone precipitation. Furthermore, the location of convective activity occurs preferentially in the warm sector early in a cyclone's life cycle, and then as the storm evolves, more convection occurs along and behind the cold front. The precipitation rates in regions with convection are more likely to be stronger than those in other precipitating regions of the cyclone. However, the cyclones with the largest area-average precipitation rates include only a small contribution from convection.

Research areas: Severe Storms
Accounting for tropical cyclones more than doubles the global population exposed to low-probability coastal flooding (2021)

Storm surges that occur along low-lying, densely populated coastlines can leave devastating societal, economical, and ecological impacts. To protect coastal communities from flooding, return periods of storm tides, defined as the combination of the surge and tide, must be accurately evaluated. Here we present storm tide return periods using a novel integration of two modelling techniques. For surges induced by extratropical cyclones, we use a 38-year time series based on the ERA5 climate reanalysis. For surges induced by tropical cyclones, we use synthetic tropical cyclones from the STORM dataset representing 10,000 years under current climate conditions. Tropical and extratropical cyclone surge levels are probabilistically combined with tidal levels, and return periods are computed empirically. We estimate that 78 million people are exposed to a 1 in 1000-year flood caused by extratropical cyclones, which more than doubles to 192 M people when taking tropical cyclones into account. Our results show that previous studies have underestimated the global exposure to low-probability coastal flooding by 31%.

Research areas: Severe Storms
The potential of spaceborne GNSS reflectometry for detecting ocean surface currents (2022)

The detectability of ocean surface currents in global navigation satellite system reflectometry (GNSS-R) observations is analyzed. We use a large dataset of spaceborne GNSS-R measurements from NASA cyclone GNSS (CYGNSS) mission. The data is collocated with ocean wind and near-surface current measurements. Our analysis reveals clear responses of the GNSS-R 0 to the presence of currents. The response depends on the wind conditions and is more prominent for wind speeds below 6 m/s. A current velocity of 0.5 m/s under an opposing wind can, on average, suppress the GNSS-R 0 by 0.8 decibels for low incidence angles. The interaction of the same current with a codirectional wind can enhance 0 by almost the same amount. This enhancement is most visible at high incidence angles. We develop a model that improves the prediction of the GNSS-R 0 in the presence of surface currents. The detected signatures of windcurrent interactions highlight the potential of GNSS-R sensors onboard small satellites for observing ocean surface currents.

Research areas: Validation
A simple approximation for the reflectance of a thick cloud in gaseous absorption band and its application for the cloud-top height determination (2019)

This paper presents a new, simple, fast method to retrieve cloud altitude from measurements of light absorption in the strongest molecular band of oxygen (the A-band), centered at 761 nm, by the polarization and directionality of the earth's reflectance sensor. First, we assess the validity of the method against synthetic spectra as a function of realistic cloud scenarios and satellite observation geometries. The retrieval error estimate amounts, on average, to less than 500 m. Second, the hurricane Ileana, overpassed the August 30, 2012, off the coasts west of Mexico and Southern California, is selected as test bed for the comparison of our retrievals against independent and nearly coincident cloud data inferred with the Moderate Resolution Imaging Spectroradiometer onboard Aqua and the Global Ozone Monitoring Experiment 2 onboard MetOp-A. We find that our approach can accurately reproduce the cloud height patterns, as long as the clouds are not thin cirrus.

Research areas: Severe Storms
Brief communication: Hurricane Dorian: Automated near-real-time mapping of the “unprecedented” flooding in the Bahamas using synthetic aperture radar (2020)

Abstract. In this communication, we present application of the automated near-real-time (NRT) system called RAdar-Produced Inundation Diary (RAPID) to European Space Agency Sentinel-1 synthetic aperture radar (SAR) images to produce flooding maps for Hurricane Dorian in the northern Bahamas. RAPID maps, released 2 d after the event, show that coastal flooding in the Bahamas reached areas located more than 10 km inland, covering more than 3000 km2 of continental area. RAPID flood estimates from subsequent SAR images show the recession of the flood across the islands and present high agreement scores when compared to Copernicus Emergency Management Service (Copernicus EMS) estimates.

Research areas: Floods
Vertical variation of tropical cyclone size in the western North Pacific (2021)

Based on the ERA5 reanalysis dataset, this paper examines the vertical variation of tropical cyclone (TC) size in the western North Pacific during 1998-2018. The TC size is defined as the distance from the TC centre to the radius at which the azimuthally averaged relative vorticity decreases to 1 × 10−5 s−1 (Rvor). It is found that TCs with similar sizes at the surface can be significantly different in size at higher levels. The Rvor at 10 m height (Rvor10) and that at 200 hPa (Rvor200) are related to TC intensity categories, and Rvor10 and that at 700 hPa (Rvor700) correlate linearly with the relative sea surface temperature (RSST) averaged within a 500-km radius. Further, a positive correlation is found between the 500-km radius averaged rain rate and Rvor200, while Rvor10, Rvor700 and Rvor200 all decrease with an increasing vertical wind shear (VWS). The spatial distributions of Rvor10, Rvor700, Rvor200 and Vmax, RSST, and rain rate are all similar to one another, and the spatial correlation coefficient between any pair of variations is larger than 0.91, which is statistically significant at the 0.01 level. The monthly variations of Rvor10, Rvor700 and Rvor200 are generally larger in the months with strong TC activity (May-October) than in the other months, although a peak of Rvor10 during March has been identified for the more recent few TCs. No significant interannual trend is found during 1998-2018 for any of the three variables (Rvor10, Rvor700 and Rvor200). Statistically significant correlations between the ENSO (El Niño-Southern Oscillation) index and Rvor10 and Rvor200 are 0.54 and 0.47, respectively, while no statistically significant correlation is found between the ENSO index and Rvor700. The mechanisms that affect the TC size at different heights are complicated and will be explored in later studies.

Research areas: Severe Storms
The influence of mid-latitude cyclones on European background surface ozone (2017)

Abstract. The relationship between springtime mid-latitude cyclones and background ozone (O3) is explored using a combination of observational and reanalysis data sets. First, the relationship between surface O3 observations at two rural monitoring sites on the west coast of Europe  Mace Head, Ireland, and Monte Velho, Portugal  and cyclone track frequency in the surrounding regions is examined. Second, detailed case study examination of four individual mid-latitude cyclones and the influence of the associated frontal passage on surface O3 is performed. Cyclone tracks have a greater influence on the O3 measurements at the more northern coastal European station, Mace Head, located within the main North Atlantic (NA) storm track. In particular, when cyclones track north of 53 N, there is a significant relationship with high levels of surface O3 (> 75th percentile). The further away a cyclone is from the NA storm track, the more likely it will be associated with both high and low (< 25th percentile) levels of O3 at the observation site during the cyclone's life cycle. The results of the four case studies demonstrate (a) the importance of the passage of a cyclone's cold front in relation to surface O3 measurements, (b) the ability of mid-latitude cyclones to bring down high levels of O3 from the stratosphere, and (c) that accompanying surface high-pressure systems and their associated transport pathways play an important role in the temporal variability of surface O3. The main source of high O3 to these two sites in springtime is from the stratosphere, either from direct injection into the cyclone or associated with aged airstreams from decaying downstream cyclones that can become entrained and descend toward the surface within new cyclones over the NA region.

Research areas: Severe Storms
On the dynamics of the eradication of a warm core mesoscale eddy after the passage of Hurricane Irma (2017) (2022)

Mesoscale oceanic eddies are known to influence air-sea interactions during tropical cyclone (TC) passage by either hindering or sustaining air-sea fluxes into the TC core. However, little is known as to how TCs alter the dynamical structure of such eddies during and after TC passage. Through simulations of Hurricane Irma (2017) using the Navys Coupled Ocean Atmospheric Mesoscale Prediction Scheme for Tropical Cyclones, it is found that a simulated mesoscale warm core eddy (WCE) located to the right of the model track disappeared shortly after the TC had passed over it. To further explore this phenomena, time series of ocean kinetic energy, available potential energy (APE), a vorticity budget, and a potential vorticity (PV) budget are examined to understand how TC-induced upper ocean currents influenced the eddy disappearance. Time series of APE within the model-simulated eddy show APE reaching a minimum as the circulation of the eddy disappeared in the model field and positive vorticity, dominated by vertical vorticity advection, became a maximum approximately 6 h after TC passage. These results were confirmed by the PV budget. The succession of subsurface vorticity changes suggest that the WCE was eradicated by a near-inertial wave wake that occurred earlier than expected. As found in a prior study, the early-onset of a near-inertial wake occurs when the model simulated TC with a small radius of maximum winds interacts with the subsurface ocean current field. The findings are important with regards to TC forecasting because the accurate representation and placement of eddies in the model field is necessary to correctly predict the coupled air-sea response during TC passage and for subsequent TCs with similar tracks. Such feedbacks from TCs can also have near-term and long-term influence on the prediction of air-sea interaction in the local and regional marine environment.

Research areas: Severe Storms
Examining the Capacity of Hurricane Matthew (2016) in Spawning Halo/Sprite‐Producible Lightning Strokes During Its Lifetime (2021)

This paper evaluated the overall capability of a hurricane in posing the electromagnetic impact on the high-altitude atmosphere. Oceanic thunderstorms are more efficient in producing negative polarity cloud-to-ground (CG) strokes with large impulse charge moment changes (iCMCs) than continental thunderstorms. As the strongest oceanic thunderstorms, hurricanes' capability to produce transient luminous events is desired to be examined. Here, we investigated the halo/sprite production of hurricane Matthew (2016) by examining the iCMCs of lightning detected by the World-Wide Lightning Location Network hour by hour at nighttime, based on the ultra-low frequency (ULF) magnetic field of the lightning strokes. Matthew was likely an active halo/sprite producer and produced more than 1,000 halo/sprite producible strokes (H/S strokes) with iCMCs exceeding the threshold (200 C km) for producing halo/sprite. The peak of H/S strokes in the outer rainband lags about one day behind the maximum hurricane strength. Additionally, the absence of positive sprite-producible strokes in the inner core (0-100 km) of Matthew may be attributed to the spiral warm cloud feature, although many negative halos could be produced instead because 112 halo/sprite producible strokes were identified here with 89% being negative. In contrast, the outer rainband exhibits some features of the trailing stratiform region of continental mesoscale convective systems (MCSs) and has been a favorable region of halo/sprite production. Overall, the inner core of Matthew and probably also that of other hurricanes bear the features that make the oceanic thunderstorms a proficient producer of negative halos but not sprites.

Research areas: Severe Storms
On the vertical extending of the explosive extratropical cyclone: A case (2021)

Explosive extratropical cyclone (EEC) is the main disastrous weather system over the ocean and offshore areas in the cold season. As a type of vertically deep system, after decades of studies, key features of EECs' vertical extents still remain vague. Based on a reasonably simulated entire-troposphere-thick EEC, this study analyzes variation of the EEC's vertical extent and investigates governing mechanisms for its vertical extending. Main findings are as follows: (a) the EEC's vertical extent showed consistent variation features with its central sea level pressure and lower-level vorticity (correlation coefficients were ~0.9), whereas its relationship with EEC's maximum surface wind was not significant; (b) EEC's upward extending featured strong ascending motion and rapid cyclonic-vorticity enhancement at the top level of the cyclone and obvious inflow (convergence) in the lower troposphere. (c) vorticity budget at the EEC's top level shows that net import transport of cyclonic vorticity (by westerly and northwesterly winds) from the trough west of the cyclone dominated its upward extending, and upward transport of cyclonic vorticity from levels below the cyclone's top level acted as the second dominant factor. In contrast, divergence-related vertical shrinking around the EEC's top level was the most detrimental factor for the cyclone's upward extending.

Research areas: Severe Storms
NASA's hurricane and severe storm sentinel (HS3) investigation (2016)

Abstract The National Aeronautics and Space Administrations (NASA) Hurricane and Severe Storm Sentinel (HS3) investigation was a multiyear field campaign designed to improve understanding of the physical processes that control hurricane formation and intensity change, specifically the relative roles of environmental and inner-core processes. Funded as part of NASAs Earth Venture program, HS3 conducted 5-week campaigns during the hurricane seasons of 201214 using the NASA Global Hawk aircraft, along with a second Global Hawk in 2013 and a WB-57f aircraft in 2014. Flying from a base at Wallops Island, Virginia, the Global Hawk could be on station over storms for up to 18 h off the East Coast of the United States and up to about 6 h off the western coast of Africa. Over the 3 years, HS3 flew 21 missions over nine named storms, along with flights over two nondeveloping systems and several Saharan air layer (SAL) outbreaks. This article summarizes the HS3 experiment, the missions flown, and some preliminary findings related to the rapid intensification and outflow structure of Hurricane Edouard (2014) and the interaction of Hurricane Nadine (2012) with the SAL.

Research areas: Severe Storms
Abiotic and biotic changes at the basin scale in a tropical dry forest landscape after Hurricanes Jova and Patricia in Jalisco, Mexico (2017)

Given the current evidence of global change, extreme events are projected to be more frequent and intense. At a river basin scale, the immediate effects of hurricanes include changes in soil properties, vegetation structure and composition, and water volume and quality, which lead to changes in species distribution and community structure. The goal of this study was to identify key abiotic and biotic elements for monitoring hurricane events at the river basin scale by linking databases of vegetation cover, small mammal diversity and water quality between 2010 and 2016. Abiotic parameters and biotic communities were monitored in a tropical dry forest (TDF) landscape on the coast of Jalisco, Mexico after two major events: Hurricanes Jova (2011) and Patricia (2015). Three zones (1-upper, 2-middle and 3-lower basin) adjacent to the TDF were analyzed along the Cuitzmala River catchment areas before and after the events. We used the Enhanced Vegetation Index (EVI) as a proxy for vegetation greenness and the diversity index of a small mammal community of rodents and bats as indicators of terrestrial habitat quality, and Fecal Coliform (FC), Fecal Enterococci (FE), and Electrical Conductivity (EC) as indicators of the river-water condition. During the years of hurricanes (2011 and 2015) there was a decrease in the EVI and small mammal diversity, as well as changes in the concentration of FC, FE and EC. The main effects associated with the two hurricanes were observed in the lower basin where hurricanes made landfall and the forest had been converted to other land uses. The EVI, communities of small mammals, and abiotic and biotic water conditions were responsive to the effects of hurricanes and can thus be useful for a long-term ecological monitoring program at the basin scale. This program would allow a faster evaluation and response to future extreme meteorological events. Our results could be implemented through the Urban and Environmental Plans at the state level (Ordenamiento Territorial del Estado de Jalisco), through the regulation of sustainable agricultural and livestock techniques, and by educating local populations of the effects of extreme meteorological events.

Research areas: Severe Storms
An introduction to the NASA East Pacific Origins and Characteristics of Hurricanes (EPOCH) field campaign (2015)

Over the past five years, tropical activity in the East Pacific has increased, while declining in the Atlantic Basin. In addition, during El Nino years, warmer than average sea surface temperatures further increase the likelihood of tropical cyclone formation in the East Pacific. Hurricane field campaigns used the Ku-/Ka-band High-Altitude Wind and Rain Airborne Profiler (HIWRAP) radar on the Global Hawk (GH) unmanned aircraft, in GRIP (Genesis and Rapid Intensification Processes 2010), HS3 (Hurricane and Severe Storm Sentinel 2012-14), and the NOAA Sensing Hazards with Operational Unmanned Technology (SHOUT 2015-16) field campaigns. Although originally designed for the GH, the X-band high-altitude RADar (EXRAD) has yet to be integrated and flown on an unmanned aerial vehicle. EXRAD will provide data with less attenuation of signal over deep convection as well as better estimates of three-dimensional winds with its nadir-pointing beam. As part of the NASA Hand On Project Experience (HOPE) Training Opportunity, our team proposed to fly the AV-6 GH aircraft with the EXRAD radar, the High Altitude MMIC Sounding Radiometer (HAMSR), and NOAA Advanced Vertical Atmospheric Profiling System (AVAPS) dropsondes to investigate genesis and/or rapid intensification (RI) of an East Pacific hurricane by measuring both the environment and interior structures. Information on planned activities primarily focused on the EXRAD high-altitude radar integration for the July-August 2017 science flight will be presented.

Research areas: Severe Storms
Government effectiveness and institutions as determinants of tropical cyclone mortality (2020)

Significance
            Tropical cyclone disasters frequently result in substantial loss of life. Institutional capacity and economic development are believed to play protective roles, but previous efforts have been unable to disentangle their relative effects. We establish empirically that stronger national and subnational institutions, independent of income, are associated with lower tropical cyclone mortality. This suggests that effective institutions play an important role in the success of disaster risk reduction strategies. Our approach of accounting for hazard intensity, population exposure, and socioeconomic conditions at high resolutions can be extended to other hazards and scales to further examine how institutions moderate risk.
          , 
            Strong institutions as well as economic development are generally understood to play critical roles in protecting societies from the adverse impacts of natural hazards, such as tropical cyclones. The independent effect of institutions on reducing these risks, however, has not been confirmed empirically in previous global studies. As a storms path and intensity influence the severity of the damages and may be spatially correlated with human vulnerabilities, failing to accurately capture physical exposure in an econometric analysis may result in imprecise and biased estimates of the influence of the independent variables. Here, we develop an approach to control for physical exposure by spatially interacting meteorological and socioeconomic data for over 1,000 tropical cyclone disasters from 1979 to 2016. We find evidence that higher levels of national government effectiveness are associated with lower tropical cyclone mortality, even when controlling for average income and other socioeconomic conditions. Within countries, deaths are higher when strong winds are concentrated over areas of the country with elevated infant mortality rates, an indicator of institutional effectiveness through public service delivery. These results suggest that policies and programs to enhance institutional capacity and governance can support risk reduction from extreme weather events.

Research areas: Severe Storms