T. H. Vonder Haar

Measurements of solar energy reflected by the earth and atmosphere from meteorological satellites

Abstract Sensors carried on the first and second generation meteorological satellites (TIROS, NIMBUS, ESSA) during the 1960s were designed to measure solar energy reflected and scattered by the earth and its atmosphere. From many months of data, a global planetary albedo of 30 per cent has been measured. Only small seasonal variations are detected on the global scale. However, much more solar energy is apparently absorbed in tropical regions than was previously believed. Application of these measurements to the total radiation and energy budgets provides a new insight into atmospheric energetics. In addition, the measurements allow quantitative study of the mean solar energy input at geographical locations, as well as temporal variations from that mean.

Solar Energy Microclimate As Determined From Satellite Observations

A method is presented for determining solar insolation at the earths surface using satellite broadband visible radiance and cloud imagery data, along with conventional in situ measurements. Conventional measurements are used to both tune satellite measurements and to develop empirical relationships between satellite observations and surface solar insolation. Cloudiness is the primary modulator of sunshine. The satellite measurements as applied in this method consider cloudiness both explicitly and implicitly in determining surface solar insolation at space scales smaller than the conventional pyranometer network.

Retrievals of mixed-phase cloud properties during the National Polar-Orbiting Operational Environmental Satellite System

We describe a novel approach developed for the National Polar-Orbiting Operational Environmental Satellite System/Visible Infrared Imaging Radiometer Suite (VIIRS) to retrieve pixel-level mixed-phase cloud optical thicknesses and effective particle sizes using 0.67, 1.6, 2.25, and 3.7 μm bands reflectance/radiance. This approach utilizes lookup tables of reflectances constructed from radiative transfer simulations and a numerical iterative search method. The capability of this new approach was demonstrated using Moderate Resolution Imaging Spectroradiometer (MODIS) data as proxy to VIIRS. Two proxy scenes, 14 October 2001 over North Platte, Nebraska, during the ninth Cloud Layer Experiment (CLEX-9) and 9 November 2006 over the Great Lakes and Eastern Canada during the Canadian CloudSat/Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations Validation Project (C3VP), were analyzed. The performance of the mixed-phase retrieval algorithm was assessed by comparison with the MODIS retrieval products, airborne in situ observations during CLEX-9 and CloudSat data during C3VP.

Measurements of the earth radiation budget from satellites during the first GARP global experiment

Abstract Two special measurements of the energy exchange between earth and space were made in connection with the FGGE. A global monitoring program using wide-field-of-view and scanner detectors from NASAs NIMBUS-7 satellite successfully returned measurements during the entire FGGE. This experiment system also used a black cavity detector to measure the total energy output of the sun to very high precision. A second set of high frequency time and space estimates of the radiation budget were determined from selected geostationary satellite data. Preliminary results from both radiation budget data sets and the solar “constant” measurements will be presented.

Measurements of absorbed shortwave energy in a tropical atmosphere

Abstract Measurements of the upward and downward solar irradiance between sea level and 20,000 feet over the tropical Atlantic have shown values of atmospheric absorption exceeding computational estimates for a cloudless sky. The disagreement between observations and calculations is greater than either the observation error or the calculation uncertainty for a gaseous atmosphere. It is a logical conclusion that the disagreement comes about from the neglect of some atmospheric constituent in the calculations. Possible explanations for the high values of absorbed solar energy include increased path length due to the scattering by aerosols or absorption by the aerosols themselves.

Meteorological satellites in support of weather modification

During the past several years, many weather modification programs have been incorporating meteorological satellite data into both the operations and the analysis phase of these projects. This has occurred because of the advancement of the satellite as a mesoscale measurement platform, both temporally and spatially, and as the availability of high quality data has increased. This paper surveys the applications of meteorological satellite data to both summer and winter weather modification programs. A description of the types of observations needed by the programs is given, and an assessment of how accurately satellites can determine these necessary parameters is made.

Large-scale precipitation estimates using satellite data; Application to the Indian Monsoon

SummaryThirty months of continuous low resolution statellite measurements of albedo and emitted longwave radiation are used to study precipitation associated with the Indian Monsoon. Combined with rainfall data for the Indian subcontinent, the satellite data are employed to develop a precipitation intensity index. It is postulated that such an index must first adequately depict the extreme monsoon rainfall regime before it can be applied to the study of rainfall over other regions, especially those devoid of conventional precipitation measurements.Three monsoons are studied to develop the index: the 1963 monsoon, the strong 1964 monsoon and the very weak 1965 monsoon. The apparently successful quantitative measure of monsoon intensity by use of the precipitation intensity index was checked using independent data for the same region in 1966 and 1969. With the aid of the index the time history of the 1964 and 1965 monsoons are examined showing how the intense cloudiness of the 1964 monsoon lingered for a number of months apparently reducing surface heating significantly preceeding the weak 1965 monsoon. This two-parameter, bi-spectral remote sensing method using satellite data can be tested for other regions using currently available satellite measurements.ZusammenfassungDreißig Monate von Satellitenmessungen niedriger Auflösegenauigkeit von Albedo und ausgehender langwelliger Strahlung wurden zu Studien der Niederschläge im Zusammenhang mit dem indischen Monsun benützt. In Kombination mit Niederschlagsdaten vom indischen Subkontinent eignen sich die Satellitendaten dazu, einen Niederschlagsintensitätsindex zu entwickeln. Es wird verlangt, daß ein derartiger Index zunächst die extremen monsunalen Regenregime zufriedenstellend beschreiben kann, bevor er auf die Niederschläge über anderen Gebieten angewendet werden kann, besonders über Gebieten, aus denen keine üblichen Niederschlagsmessungen vorhanden sind.Drei Monsunperioden wurden zur Ableitung dieses Index herangezogen: der Monsun von 1963, der starke Monsun von 1964 und der sehr schwache Monsun von 1965. Die offensichtlich erfolgreiche quantitative Abschätzung der Monsunintensität unter Verwendung des Niederschlagsintensitätsindex wurde mittels unabhängiger Daten von derselben Region für die Jahre 1966 und 1969 überprüft. Mit Hilfe dieses Index wird die zeitliche Entwicklung des Monsuns während der Jahre 1964 und 1965 untersucht, wobei sich zeigt, daß die intensive Bewölkung des Monsuns im Jahre 1964 eine Reihe von Monaten anhielt und offensichtlich die Bodenerwärmung vor der schwachen Monsunperiode 1965 signifikant verminderte. Diese auf zwei Parametern und zwei Spektralbereichen begründete Satellitenmeßmethode kann nunmehr für andere Gebiete verwendet werden, wofür die dazu erforderlichen Satellitendaten derzeit bereits erhältlich sind.

NPOESS soil moisture satellite data assimilation: Progress using WindSat data

In this work, we have developed a four-dimensional coupled atmospheric/land data assimilation framework using the Regional Atmospheric Modeling Data Assimilation System (RAMDAS) to retrieve deep soil moisture profiles. Passive microwave data from CORIOLIS WindSat are used as a surrogate for future National Polar-orbiting Operational Environmental Satellite System (NPOESS) microwave sensors. Current efforts are focused on the use of the system for a case study occurring in September 2003.

NPOESS Soil Moisture Satellite Data Assimilation and RFI Mitigation: Use of WindSat Data and a Discrete Backus-Gilbert Technique

This work develops (1) a four-dimensional data assimilation methodology to retrieve deep soil moisture profiles using the National Polar-orbiting Operational Environmental Satellite System (NPOESS) and other associated data, (2) a methodology for better spatial mapping of the masking effects caused by surface features (i.e., vegetative cover and surface roughness), and (3) a discrete Backus-Gilbert (DBG)-based methodology for reducing the radio frequency interference impacts at 6.7 and 10 GHz.

Microwave surface emittance retrieval using coincident microwave and infrared satellite data

Two methods are used to calculate microwave surface emittance using the Special Sensor Microwave/Imager (SSM/I) data and the GOES Visible Infrared Spin Scan Radiometer (VISSR) data. The first method calculates an effective surface emittance using only the microwave and infrared brightness temperatures and uses the infrared data as a near-blackbody temperature reference. This method does not account for atmospheric attenuation in the infrared or microwave frequencies. A second more rigorous method includes an atmospheric correction for water vapor attenuation. Comparisons are made between the methods followed by a discussion of the practical implications of the results.