Intensive Field Observations Research Articles

Modeling microwave interactions with crops and comparison with ERS-2 SAR observations

A comprehensive multilayer second-order radiative transfer model, driven entirely by intensive field observations, is used to show that second order terms contribute at most 0.5 dB to the backscattering coefficient at all polarizations from wheat and barley throughout the growing season and 1 dB to the copolar response of oilseed rape. Under these circumstances, an equivalent integrable first-order model, with coefficients derived from full model runs, can be formulated. This allows the role of each of the plant components in attenuating and scattering the radar signal to be clarified, and provides a basis for quantitative comparison of observed ERS-2 backscatter values with model calculations, taking full account of measurement uncertainties. Discrepancies between the two suggest that effective attenuation through mature cereal crops is overestimated by the model. This appears to be either an intrinsic failure of the radiative transfer formulation or (more likely) due to an inadequate adaptation of the notion of crop coverage to the microwave case. Nonplanarity of leaves is an important source of model error for oilseed rape.

FIELD EXPERIMENT AND OBSERVATIONS OF RUNOFF GENERATION PROCESSES IN A FORESTED MOUNTAINOUS CATCHMENT, TONO AREA, JAPAN

The present paper shows the relevance of a new approach of using back propagation neural network (BPNN) in storm runoff estimation by using near surface soil moisture. Intensive field observation and field experiment conducted to observe the behavior of a forested catchment in Tono area is presented. The results obtained by numerical experiment using BPNN were tested by the field experiment and catchment observations. Both the experiment and field observations supported the results of the previous studies. The field experiment showed that the importance of litter layer in the direct contribution to runoff was not so significant. It was observed that the highly conductive soil layer underlying the litter layer and overlying the less macroporous soil zone with low hydraulic conductivity was the chief contributor to the total runoff in the study area. The field observation showed that the main contribution to the total storm runoff was from the channel system that received the runoff from such layers as in the field experiment.

DENSITY INFLUENCES CENSUS TECHNIQUE ACCURACY FOR CERULEAN WARBLERS IN EASTERN ONTARIO

Abstract This study investigated the accuracy of 50-m fixed-radius, 100-m fixed-radius, and variable circular-plot point counts to estimate the actual density of breeding Cerulean Warblers (Dendroica cerulea) during the 1997 and 1998 breeding seasons, in Ontario, Canada. Density estimates were compared to actual densities as measured from intensive field observation of pairing and nesting behavior. Estimates of density from each of the techniques were positively correlated with actual density in both years. Both the technique used to census a population as well as the actual density of the population itself affected the accuracy of the derived density estimations. In both years, the 50-m fixed-radius technique overestimated density. In contrast, the 100-m fixed-radius technique and variable circular-plot technique underestimated density; the degree of the underestimate of the 100-m fixed-radius increased as actual density increased. There was no correlation between the degree of underestimation and actual...

Remote sensing of cirrus cloud parameters based on a 0.63‐3.7 µm radiance correlation technique applied to AVHRR data

Using the data gathered from the Advanced Very High Resolution Radiometer (AVHRR) 0.63 and 3.7 µm channels, an algorithm for the inference of cirrus cloud optical depth and mean effective size has been developed for the first time. This scheme is based on the correlation between the 3.7 µm (total) and 0.63 µm radiances that is constructed from radiative transfer calculations involving ice crystal clouds. Application of the algorithm to AVHRR channels has been performed by using data sets that were collected during the First ISCCP Regional Experiment, Phase II, Cirrus Intensive Field Observation (FIRE‐II‐IFO; November–December 1991) at Coffeyville, Kansas. For validation, the in‐situ data collected by the balloon‐borne replicator and airborne 2‐D probes that were collocated with AVHRR pixels were carefully analyzed for five cases involving single and multiple cirrus cloud layers. We demonstrate that the retrieved cirrus cloud optical depths and mean effective sizes compare reasonably well with those determined from the in‐situ analyses.

Genetic susceptibility testing: ethical and social quandaries.

Breast cancer in the United States continues to be a serious public health problem that affects individuals, families, and society. The simultaneous rapid progress in mapping the human genome, the advances in technology, and the subsequent commercialization of genetic testing have made it possible for women to seek breast and ovarian cancer susceptibility testing before comparable social and psychological supports are put in place. As health care places more emphasis on illness prevention and simultaneously commits less economic support for health care, genetic testing presents social and ethical challenges as well as dilemmas. The study discussed in this article consisted of intensive field observation and in-depth, face-to-face interviews concerning genetic susceptibility testing. The social worker may be in a unique position to collaborate with other health professionals in the clinical and the policy arena in regard to these tests.

Status of desertification in the Patagonian region: Assessment and mapping from satellite imagery

Desertification advance in the Patagonian region is the main socioecological problem. However, in this region the precise location, extent, severity, and characteristics of desertification are often unknown. The objectives of this research were (1) to evaluate, classify, and interpret the status of desertification, based on biological and physical indicators in the Patagonian arid, semiarid, and subhumid region of Argentina; (2) to develop a map of desertification with recommendations for decision makers; and (3) to create a methodology to determine accurately the distribution of land degradation from satellite imagery. Data were obtained from selected cloud‐free scenes of the National Oceanographic and Atmospheric Administration/Advanced Very High Resolution Radiometer “large‐area coverage” (NOAA/AVHRR LAC), existing data, and intensive field observations. The combination of the coarse‐resolution satellite data of this study with fine‐resolution satellite data [Landsat multispectral scanner (MSS)] were the basis for the region‐wide assessment of desertification status. From the total region studied (78.5 million ha), 93.6% (73.5 million ha) showed different degrees of desertification. Categories of desertification for the whole region were slight (9.3%), moderate (17.1%), moderate to severe (35.4%), severe (23.3%), and very severe (8.5%). The provinces where reclamation and/or control measures should be applied are, in order of priority, Santa Cruz, Neuquén, Chubut, Río Negro, and Tierra del Fuego archipelago. Considering the lack of a common management strategy among the provinces, it is recommended (1) to give importance to landscape diversity when managing natural resources, (2) to suggest alternative livestock grazing schemes and management of the environmental heterogeneity, (3) to revegetate or restore degraded areas, (4) to declare some areas Provincial Reserves, and (5) to exclude livestock and collection of firewood either temporarily or permanently.

The Role of Ice Particle Shapes and Size Distributions in the Single Scattering Properties of Cirrus Clouds

Abstract The roles of ice particle size distributions (SDs) and particle shapes in cirrus cloud solar radiative transfer are investigated by analyzing SDs obtained from optical array probe measurements (particle sizes larger than 20–40 μm) during intensive field observations of the International Cirrus Experiment, the European Cloud and Radiation Experiment, the First ISCCP Regional Experiment, and the Central Equatorial Pacific Experiment. It is found that the cloud volume extinction coefficient is more strongly correlated with the total number density than with the effective particle size. Distribution-averaged mean single scattering properties are calculated for hexagonal columns, hexagonal plates, and polycrystals at a nonabsorbing (0.5 μm), moderately absorbing (1.6 μm), and strongly absorbing (3.0 μm) wavelength. At 0.5 μm (1.6 μm) (3.0 μm), the spread in the resulting mean asymmetry parameters due to different SDs is smaller than (comparable to) (smaller than) the difference caused by applying diff...

Baroclinic eddies south of Cheju Island in the East China Sea

The detailed structures of baroclinic eddies, that is, an anticlockwise circulation in the upper layer and a clockwise one in the lower layer south of Cheju Island in the East China Sea have been revealed by intensive field observation. Such baroclinic eddies are accompanied by the southward spreading of the Yellow Sea Bottom Cold Water.

Numerical Simulations of the Marine Stratocumulus-Capped Boundary Layer and Its Diurnal Variation

Abstract A high-resolution one-dimensional version of a second-order turbulence radiative–convective model, developed at Los Alamos National Laboratory, is used to simulate the diurnal cycle of the marine stratocumulus cloud-capped boundary layer. The fidelity of the model to the underlying physics is assessed by comparing the model simulation to data taken at San Nicolas Island during the intensive field observation (IFO) of the First International Satellite Cloud Climatology Project (ISCCP) Regional Experiment (FIRE), conducted during June and July 1987. The model is able to reproduce the observed diurnal cycle of the liquid water content, cloud-base height, radiative heating or cooling rates, and the mean and turbulence variables fairly well. The mechanisms that cause the diurnal variation and the decoupling of the boundary layer are examined. The possible role of an imposed diurnal cycle for the subsidence in inducing the cloud-top diurnal cycle observed during the FIRE IFO is also addressed. Three re...

Soil-water behaviour in a push terminal moraine: comparison of one- and two-dimensional simulations based on intensive regional field observations

To predict the contamination risk of drinking water in a water catchment, regionalization methods, in which regional transferability is presupposed by assigning areas of same qualities, are used. Those methods use soil information at the field scale to build up soil profiles, which serve as input for one-dimensional simulation models of water and solute transport together with management data. These simulation models compute groundwater recharge to determine the transport and contamination risk of solutes. The regionalization method assumes horizontal homogeniety and one representative soil profile (principal profile) for each soil mapping unit. Our objective is to show that those regionalization methods have to be improved in regions of high spatial variability of soil qualities. As an example we examine a terminal moraine typical of northern Germany. We combine intensive investigations of the soil structure, long-time field observations and simulation results to show the necessity to improve methods for soil mapping. Our results suggest that it is necessary to perform higher-dimensional simulations of water and solute transport in regions of high spatial soil structure variability. Two-dimensional simulations compute earlier and higher groundwater recharge rates than one-dimensional simulations.

Detection of Multilayer Cirrus Cloud Systems Using AVHRR Data: Verification Based on FIRE II IFO Composite Measurements

Abstract A numerical scheme has been developed to identify multilayer cirrus cloud systems using Advanced Very Higher Resolution Radiometer (AVHRR) data. It is based on the physical properties of the AVHRR channels 1–2 reflectance ratios, the brightness temperature differences between channels 4 and 5, and the channel 4 brightness temperatures. In this scheme, clear pixels are first separated from cloudy pixels, which are then classified into three types: cirrus, cirrus/low cloud, and low clouds. The authors have applied this scheme to the satellite data collected over the FIRE II IFO [First ISCCP (International Satellite Cloud Climatology Project) Regional Experiment II intensive field observations area during nine overseas within seven observation dates. Determination of the threshold values used in the detection scheme are based on statistical analysts of these satellite data. The authors have validated the detection results against the cloudy conditions inferred from the collocated and coincident grou...

Optical Depth Measurements of Aerosol Cloud, and Water Vapor Using Sun Photometers during FIRE Cirrus IFO II

Abstract Optical depths in the visible to infrared spectral region were obtained from solar extinction measurements with two sun photometers during the First ISCCP Regional Experiment Phase II Cirrus Intensive Field Observation in Kansas. A method is described to correct sun photometry for gaseous absorption and is extended to estimate the water vapor amount. The approach uses a prior computation of gaseous absorption for the narrowband-pass sun photometry, parameterized with the slant-path absorber amount. These produce correction coefficients for gaseous absorption, as determined by LOWTRAN 7 models. Near-infrared channels were calibrated by modified Langley plots taking account of gaseous absorption. After the correction and calibration, the aerosol optical depths at the wavelength of 0.4–4 µm were obtained for clear sky conditions. The aerosol optical depth at the wavelength λ = 0.5 µm was 0.1–0.2 during the campaign. The cloud optical depth at λ = 0.5 µm was obtained for cirrus events on 26 November ...

A Comparison of Columnar Water Vapor Retrievals Obtained with Near-IR Solar Radiometer and Microwave Radiometer Measurements

Abstract A simple two-channel solar radiometer and analysis technique have been developed for setting atmospheric water vapor via differential solar transmission measurements in and adjacent to the 940-nm water vapor absorption band. A prototype solar radiometer developed for the National Oceanic and Atmospheric Administration (NOAA)/Environmental Research Laboratory underwent trial measurements near Boulder, Colorado, and during the First ISCCP (International Satellite Cloud Climatology Project) Regional Experiment Phase II cirrus intensive field observation program (Coffeyville, Kansas). These measurements provided the convenient opportunity to compare solar radiometer water vapor retrievals with those obtained using NOAA microwave radiometers. The solar radiometer and microwave radiometer retrievals were found to agree to within 0.1 cm most of the time and to within 0.05 cm the majority of the time, yielding a percent difference in the retrievals generally within 10%. Radiosonde soundings, when availab...

Removal of the Solar Component in AVHRR 3.7-µm Radiances for the Retrieval of Cirrus Cloud Parameters

Abstract A numerical scheme has been developed to remove the solar component in the Advanced Very High Resolution Radiometer (AVHRR) 3.7-µm channel for the retrieval of cirrus parameters during daytime. This method uses a number of prescribed threshold values for AVHRR channels 1 (0.63 µm), 2 (0.8 µm), 3 (3.7 µm), 4 (10.9 µm), and 5 (12 µm) to separate clear and cloudy pixels. A look-up table relating channels 1 and 3 solar reflectances is subsequently constructed based on the prescribed mean effective ice crystal sizes and satellite geometric parameters. An adding–doubling radiative transfer program has been used to generate numerical values in the construction of the look-up table. Removal of the channel 3 solar component is accomplished by using the look-up table and the measured channel 1 reflectance. The cloud retrieval scheme described in Ou et al. has been modified in connection with the removal program. The authors have applied the removal–retrieval scheme to the AVHRR global area coverage daytime data, collected during the First ISCCP (International Satellite Cloud Climatology Project) Regional Experiment cirrus intensive field observation (FIRE IFO) at 2100 UTC 28 October 1986 over the Wisconsin area. Distributions of the retrieved cloud heights and optical depths are comparable to those determined from Geostationary Operational Environmental Satellite visible and IR channels data reported by Minnis et al. Morwver, verifications of the retrieved cirrus temperature and height against lidar data have been carried out using results reported from three FIRE IFO nations. The retrieved cloud heights are within 0.5 km of the measured lidar values.

冬季南西諸島海域における層状雲の雲物理学的性質

Microphysical properties of stratiform clouds were observed over the Southwest Islands Area as a part of intensive field observations of Western North-Pacific Cloud-Radiation Experiments (WENPEX). The observation was made under the weak outbreak of cold airmass in January 1991. The observed clouds were mainly stratocumulus clouds, whose cloud depths were about 0.5 to 1.2 Km. A strong temperature inversion was always observed near the cloud tops, above which there was a stable dry layer. The air temperature near cloud tops reached values lower than 0°C for some clouds (minimum temperature: -5°C). The clouds consisted mainly of cloud droplets and they were non-precipitating clouds. The clouds showed considerable horizontal inhomogeneity and vertical changes. The number concentration of cloud droplets in the central parts of clouds showed a tendency to be constant with height. The mean concentration reached approximately 500 to 800 cm -3 as a result of a high CCN concentration. Mean droplet radius rose from about 3 μm near cloud base to 7 μm near cloud top. The vertical profiles of liquid water content (LWC) indicated that the values increased with height as a result of an increase in droplet size rather than concentration. The peak LWC reached about 1.0 g/m 3 in the thick clouds. The envelope of maximum LWC was generally smaller than the adiabatic values. Effective radius changed from about 3 μm near cloud base to 6 μm near cloud top. The characteristics of the stratocumulus clouds over the Southwest Islands Area in Japan is discussed from the microphysical standpoint, as compared with the stratiform clouds observed in geographically different areas.

Microphysical characteristics of a marine stratiform cloud obtained from lidar and in situ measurements

Abstract Lidar and in situ aircraft measurements were performed in a marine stratiform layer during the intensive field observation of the International Cirrus Experiment (ICE 89). The analysis of the results shows that this marine boundary layer is mainly characterized by two decoupled stratiform cloud layers. Drizzle formation is evidenced to be efficient on an horizontal scale ranged between 20 and 30 km in the upper stratiform cloud and promotes depletion of the cloud water. The drops are large enough to fall through the lower layer without evaporation. Subsequent differences in microphysical properties between cloud and drizzle regions are clearly evidenced and may have a strong influence on visible optical depth and cloud albedo. The calibration of the Lidar data we propose leads to describe the vertical microstructure of the precipitating drizzle regions.

Microphysical modeling of cirrus: 1. Comparison with 1986 FIRE IFO measurements

We have used a one‐dimensional model of cirrus formation to study the development of cirrus clouds during the 1986 First ISCCP (International Satellite Cloud Climatology Project) Regional Experiment (FIRE) intensive field observations (IFO). The cirrus model includes microphysical, dynamical, and radiative processes. Sulfate aerosols, solution drops, ice crystals, and water vapor are all treated as interactive elements in the model. Ice crystal size distributions are fully resolved based on calculations of homogeneous freezing nucleation, growth by water vapor deposition, evaporation, coagulation, and vertical transport. We have focused on the cirrus observed on November 1, 1986. Vertical wind speed for the one‐dimensional simulation is taken from a mesoscale model simulation for the appropriate time period. The mesoscale model simulation suggested that strong upward motions over Wyoming and subsequent horizontal transport of upper level moisture were responsible for the cirrus observed over Wisconsin on this date. We assumed that our one‐dimensional model could be used to represent a vertical column moving from Wyoming to Wisconsin over a period of several hours. Ice crystal nucleation occurs in our model in the 8 to 10‐km region as a result of the strong updrafts (and cooling) early in the simulation. Growth, coagulation, and sedimentation of these ice crystals result in a broad cloud region (5–10 km thick) with an optical depth of 1–2 after a few hours, in agreement with the FIRE measurements. Comparison with aircraft microphysical measurements made over Wisconsin indicates that the simulation generated reasonable ice water content, but the predicted ice number densities are too low, especially for radii less than about 50 μm. Sensitivity tests suggest that better agreement between simulated and observed microphysical properties is achieved if the nucleation rate is higher or stronger vertical mixing (perhaps associated with multidimensional motions) is present.

Mesoscale Numerical Simulation of Cirrus Clouds—FIRE Case Study and Sensitivity Analysis

The 28 October 1986 First ISCCP (International Satellite Cloud Climatology Program) Regional Experiment (FIRE) case was simulated using the Regional Atmospheric Modeling System developed at Colorado State University. This three-dimensional mesoscale model was applied in nonhydrostatic and nested-grid mode, using explicit, bulk microphysics and radiation. The simulation resulted in very good agreement between observed and model-predicted dynamic and cloud fields. Cloud height, thickness, areal extent, and microphysical composition were verified against GOES satellite imagery, lidar, and aircraft measurements taken during the FIRE cirrus intensive field observation. Cloud-top generation zones and layering were simulated. Sensitivity simulations were run to determine long- and shortwave radiative forcing. Also, a simulation was run with no condensate to examine cloud feedbacks on the environment. Longwave radiation appeared to be instrumental in developing weak convective-like activity, thereby increasing the cloud's optical depth.

Stratocumulus Cloud Properties Derived from Simultaneous Satellite and Island-based Instrumentation during FIRE

Cloud parameters derived from visible and infrared window data from the Geostationary Operational Environmental Satellite (GOES) are compared to corresponding properties determined from instrumentation on San Nicolas Island off the coast of California during the First ISCCP Regional Experiment marine stratocumulus intensive field observations period in July 1987. Examination of the satellite imagery revealed that the apparent bias can be explained by the persistence of the clouds over the northwest part of the island during periods of clearing around the island. Diurnal variations in the cloud cover were very significant; minimum cloudiness occurred during the late afternoon and maximum cloudiness early in the morning. Relationships were established between the satellite-derived cloud optical depth and two surface-observed quantities: cloud liquid water path and cloud thickness. Simultaneous observations of liquid water path and satellite-derived cloud optical depth were used to infer effective cloud-droplet radius, resulting in good agreement with correlative data. The diurnal variations in cloud amount are accompanied by changes in cloud thickness, cloud-top height, cloud liquid water path, and effective droplet size. These observations provide the most complete picture, to date, of the diurnal cycle of marine stratocumulus clouds, confirming previous satellite-based inferences of the diurnal behavior of marine stratocumulus at larger scales.

Reflectivities of uniform and broken layered clouds

1 km AVHRR imagery data from the NOAA satellites, collected during the FIRE Marine Stratocumulus Intensive Field Observations, were used to determine differences between the reflectivities of uniform, layered clouds and those of broken clouds taken from the same layers. Observations for the 0.63 µ m channel indicated that regardless of the viewing geometry obtained with the polar orbiters, the average reflectivities of broken clouds were approximately 80–85% of the reflectivities of the same clouds when they formed uniform layers. Furthermore, the anisotropy of radiation reflected by uniform clouds appeared to be no different than that reflected by the broken clouds. Consequently, if the uniform, layered clouds observed in this study reflect according to plane-parallel theory, then the reflectivities of broken clouds could be approximated by simply reducing the values obtained with plane-parallel theory. For observations in the 3.7 µ m channel, the average reflectivities of the broken clouds were generally larger than the reflectivities of the uniform, layered clouds. Furthermore, the anisotropy of radiation reflected by broken clouds differed from that of the radiation reflected by uniform clouds. The reduced reflectivity at visible wavelengths for broken clouds may explain the 10% discrepancy between pre-satellite era estimates of the earth's albedo and satellite estimates. Furthermore, while the differences in reflectivities between uniform and broken clouds are qualitatively consistent with Monte Carlo simulations of finite cloud effects, they are also consistent with plane-parallel radiative transfer models in which the central portions of clouds contain relatively large concentrations of liquid water distributed among relatively large droplets, while the edges of clouds contain relatively low concentrations of liquid water distributed among relatively small droplets. DOI: 10.1034/j.1600-0889.1991.t01-3-00008.x