New observations of Bolivian wind streaks by JPL Airborne SAR: Preliminary results

In 1993 NASA's Jet Propulsion Laboratory Airborne Synthetic Aperture Radar system (AIRSAR) was deployed to South America to collect multi-parameter radar data over pre-selected targets. Among the sites targeted was a series of wind streaks located in the Altiplano of Bolivia. The objective of this investigation is to study the effect of wavelength, polarization, and incidence angle on the visibility of wind streaks in radar data. Because this is a preliminary evaluation of the recently acquired data we will focus on one scene and, thus, only on the effects of wavelength and polarization. Wind streaks provide information on the near-surface prevailing winds and on the abundance of winderodible material, such as sand. The potential for a free-flyer radar system that could provide global radar images in multiple wavelengths, polarizations, and incidence angles requires definition of system parameters for mission planning. Furthermore, thousands of wind streaks were mapped from Magellan radar images of Venus; their interpretation requires an understanding of the interaction of radar with wind streaks and the surrounding terrain. Our experiment was conducted on wind streaks in the Altiplano of Bolivia to address these issues

Summaries of the Fifth Annual JPL Airborne Earth Science Workshop. Volume 3: AIRSAR Workshop

This publication is the third containing summaries for the Fifth Annual JPL Airborne Earth Science Workshop, held in Pasadena, California, on January 23-26, 1995. The main workshop is divided into three smaller workshops as follows: (1) The Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) workshop, on January 23-24. The summaries for this workshop appear in Volume 1; (2) The Airborne synthetic Aperture Radar (AIRSAR) workshop, on January 25-26. The summaries for this workshop appear in this volume; and (3) The Thermal Infrared Multispectral Scanner (TIMS) workshop, on January 26. The summaries for this workshop appear in Volume 2

Spacelab Science Results Study

Beginning with OSTA-1 in November 1981 and ending with Neurolab in March 1998, a total of 36 Shuttle missions carried various Spacelab components such as the Spacelab module, pallet, instrument pointing system, or mission peculiar experiment support structure. The experiments carried out during these flights included astrophysics, solar physics, plasma physics, atmospheric science, Earth observations, and a wide range of microgravity experiments in life sciences, biotechnology, materials science, and fluid physics which includes combustion and critical point phenomena. In all, some 764 experiments were conducted by investigators from the U.S., Europe, and Japan. The purpose of this Spacelab Science Results Study is to document the contributions made in each of the major research areas by giving a brief synopsis of the more significant experiments and an extensive list of the publications that were produced. We have also endeavored to show how these results impacted the existing body of knowledge, where they have spawned new fields, and if appropriate, where the knowledge they produced has been applied

Spatial and Temporal Development of Saltation in Air.

PhDA resurgence of interest in the concept of equilibrium in the aeolian saltation system has been witnessed in the 1990's. Throughout the aeolian field of research, i. e. wind tunnel, field and numerical models, many highly successful individual investigations have been conducted. Despite these data, however, the timing and location of the mass flux equilibrium have not been quantified. This research investigates the simultaneous downwind spatial and temporal developments of the aeolian saltation system. Experiments were conducted in the laboratory and the field. By unification of the spatial and temporal dimensions in both environments one of the major limitations of contemporary aeolian science, the inability to relate data from different experimental environments, is addressed. In the wind tunnel the development of the saltation system was measured over a streamwise length of 8m. Sediment transport was measured at 1m intervals by the downwind deployment of seven Aarhus sand traps. In the field the development of the saltation system was monitored over distances of 10m and 20m. Mass flux was measured by the downwind deployment of five 'total load' sand traps. In both environments temporal wind velocity and mass flux data were collected simultaneously at a single site. Spatial profile velocity data were later obtained by a streamwise traverse along the experimental area. The downwind spatial development of the saltation system, from a point of initiation, in the laboratory and the field is manifest by an overshoot in mass flux and shear velocity. It is shown that in both environments mass flux increases with distance to a maximum at 4m downwind. This result is in remarkable agreement with existing data of a comparable scale. In the wind tunnel and the field experiments it V' is found that shear velocity overshoots between 2-4m downwind of the overshoot in mass flux. The distance between the overshoot in mass flux and the overshoot in shear velocity is termed the 'separation distance'. The existence of a 'separation distance' between the overshoots of mass flux and shear velocity questions the appropriateness of traditional mass flux formulae. It is found that conventional mass flux relationships with shear velocity, generated from data collected simultaneously at the same site, have the lowest predictive capability. The greatest confidence in the ability of shear velocity to predict the rate of mass flux is shown to occur when shear velocity data are collected downwind of mass flux data. The critical distance between the data collection points is demonstrated to be defined by the 'separation distance'. The downwind spatial development of the saltation system without a point of initiation in the laboratory and the field is influenced by sand entering from upwind. The existence of high energy bombardment by saltation processes throughout the experimental area is shown to produce an accelerated development of the saltation system. It is found that the precise downwind development of mass flux and shear velocity are dependent on the exact rate of sand entering from upwind. The temporal development of the saltation system is controlled essentially by the availability of transportable grains from the sand bed. In both the wind tunnel and the field experiments it is demonstrated that the saltation system develops through time from a transport-limited to a supply-limited system. The depletion of the sand bed through time limits the existence of the state of equilibrium. The equilibrium concept is thus shown to be inappropriate for the universal prediction of mass flux

Mapping wetland areas on forested landsacpes using Radarasat-2 and Landsat-5 TM data

Wetlands are an important ecosystem for many vital functions such as groundwater recharge, flood control, water quality improvement, and to mitigate erosion. Monitoring and mapping wetlands on a large scale is becoming increasingly more important, and satellite remote sensing provides a practical approach. This study examines the potential for using multi-beam Radarsat-2 C-band polarimetric SAR, Landsat-5 TM, and DEM data for classifying wetland and non-wetland classes in a forested watershed in Ontario, Canada. It investigates the influence of incidence angle, leaf presence and moisture conditions in the classification of SAR images. The images were classified using two classification methods: the Maximum Likelihood Classifier and Random Forests classifier. Lastly, SAR polarimetric variables and decompositions were investigated for their usefulness in classification. Fourteen Radarsat-2 Fine Quad (FQ) SAR images were acquired from October 2010 to November 2011 at different incidence angles but with the same orbit-descending pass (west-looking direction). The images were paired according to the beam mode (FQ4 and FQ22/27), leaf presence (off and on) and moisture (wet/dry) conditions. The FQ image pair which gave the best classification overall accuracy (76.3%) using the Maximum Likelihood classification was those from the two FQ22/27 images acquired under leaf-off and dry conditions. When the FQ images were classified together with five optical bands of a Landsat image, the classification accuracy was higher for all classes as well as for the overall accuracy (94.4%). When the FQ images were combined with the Landsat image and slope, overall accuracy improved only slightly from the FQ and Landsat combination (95.4%). With the Random Forests classification, the best overall accuracy was obtained with the combination of the FQ 22/27 image pair acquired under leaf-off and dry image conditions, Landsat and slope (98.7%), followed closely by the FQ pair and Landsat combination (98.6%). When all FQ images were used as input to the Random Forests classification, this also produced high cross-validation overall accuracies (98.3%), indicating that while Landsat does add accuracy FQ images can give comparable accuracies if the right dates and conditions are chosen. A benefit of using Random Forests is the ability to rank band importance in image classification. From this it was determined that using multiple FQ images with leaf-off conditions were preferred. As for the other conditions, a mix of incidence angles, moisture conditions, and polarizations were important for classification. The incoherent target decompositions were the most important polarimetric variable in the classification, while the only other parameter indicated as important from both classifications was the orientation angle for the maximum of the completely polarized component. In future studies, it may be of interest to test the combination of multi-date polarimetric variables and decompositions parameters together with all polarizations (HH, HV, VH, and VV). So far, we classified only two types of wetlands (closed and open). Further studies are needed to test the Random Forests classifier for classifying the wetlands into more detailed classes (bog, fen, marsh, swamp, etc.). Lastly, future studies should test the results found here using independent evaluation data to assess the accuracy

Identifying mineral dust emission sources in the Middle East using remote sensing techniques

This investigation presents a new high-resolution mineral dust climatology for the Middle East, describing the dust emission source of over 27,000 dust emission events during the period 2006 – 2013. The inventory was derived from the dust RGB product of the Spinning Enhanced Visual and InfraRed Imager (SEVIRI) on-board Meteosat’s second-generation satellite (MSG). Mineral dust emissions were derived from visual inspection of the SEVIRI scenes, which have 4-5 km2 spatial and 15-minute temporal resolution. The location of every emission event was recorded in a database, along with time and trajectory of dust movement. This is an improvement on previous studies, which derive dust source areas from the daily observations of Aerosol Optical Depth whose maxima do not necessarily coincide with sources of emissions, producing more accurate information on the location of the important dust sources in the region. Results showed that dust sources are constrained to relatively small areas, with 23% of dust emissions generated from areas covering just 1% of the total land surface of the Middle East. Important sources include the Tigris-Euphrates flood plains of Iraq and Syria, Western and Northern Saudi Arabia and the Sistan Basin in Eastern Iran. The Tigris-Euphrates flood plain was the most active dust region, producing 37% of all dust events. Here, agricultural surfaces, especially those producing rain-fed wheat and barley appear to be particularly sensitive to drought conditions, with greatest dust emission frequency at the peak of the 2007 – 2009 drought – the most severe drought in instrumental history. Normalised Difference Vegetation Index (NDVI) data was acquired from the Moderate Resolution Imaging Spectrodiometer (MODIS) (MOD13A2) 1km database and correlated with dust emission frequency data in the region of greatest dust activity. These dust emission ‘hotspots’ showed a significant correlation between vegetation cover and dust emission frequency, with increased vegetation cover during non-drought years producing a marked decrease in dust emission frequency. The southern areas of the Arabian Peninsula recorded very few dust emission observations, contrasting directly to many previous studies, which do not use such high temporal resolution data. The activation and frequency of dust emissions are characterised by strong seasonality developing in response to specific synoptic conditions. ERA Interim reanalysis data were used to characterise synoptic conditions on identified dusty days, demonstrating a concurrent increase in dust emission frequency with intensifying summer (JJA) Shamal (northerly) winds over the Arabian Peninsula