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Abstract
Radar has been used to study insect flight for over 20 years. Radar, especially airborne radar, is unrivaled in its ability to observe the spatial organization of insect migration. This paper reports methods of data collection and analysis used by current airborne entomological radar systems and, in particular, the method used to review the data collected and visualize any large-scale structures detected. Examples of data from recent U.S. Department of Agriculture field experiments are presented to illustrate the analysis techniques. The data review method allows further data collection and analysis to be focused on areas of particular interest and thus significantly enhances the utility of airborne entomological radar.
Abstract
Radar has been used to study insect flight for over 20 years. Radar, especially airborne radar, is unrivaled in its ability to observe the spatial organization of insect migration. This paper reports methods of data collection and analysis used by current airborne entomological radar systems and, in particular, the method used to review the data collected and visualize any large-scale structures detected. Examples of data from recent U.S. Department of Agriculture field experiments are presented to illustrate the analysis techniques. The data review method allows further data collection and analysis to be focused on areas of particular interest and thus significantly enhances the utility of airborne entomological radar.
Abstract
This note focuses on a new method of analysis, suitable for use with data from satellite microwave spectrometers, that may benefit hydrometeorological analysis and prediction. The method being proposed involves application of spectral microwave and infrared data such as available from the Nimbus 6 SCAMS/HIRS and Nimbus 5 ESMR experiments, or similar data forthcoming from Nimbus G and TIROS-N, to examine the moisture budget of storm areas over oceans.
Exploratory computations obtained by testing the proposed technique on a limited sample of available data are presented. Capabilities and limitations are noted.
Abstract
This note focuses on a new method of analysis, suitable for use with data from satellite microwave spectrometers, that may benefit hydrometeorological analysis and prediction. The method being proposed involves application of spectral microwave and infrared data such as available from the Nimbus 6 SCAMS/HIRS and Nimbus 5 ESMR experiments, or similar data forthcoming from Nimbus G and TIROS-N, to examine the moisture budget of storm areas over oceans.
Exploratory computations obtained by testing the proposed technique on a limited sample of available data are presented. Capabilities and limitations are noted.
Abstract
The International Advanced Television and Infrared Observation Satellite Operational Vertical Sounder (ATOVS) Processing Package (IAPP) has been developed to retrieve the atmospheric temperature profile, moisture profile, atmospheric total ozone, and other parameters in both clear and cloudy atmospheres from the ATOVS measurements. The algorithm that retrieves these parameters contains four steps: 1) cloud detection and removal, 2) bias adjustment for ATOVS measurements, 3) regression retrieval processes, and 4) a nonlinear iterative physical retrieval. Nine (3 × 3) adjacent High-Resolution Infrared Sounder (HIRS)/3 spot observations, together with Advanced Microwave Sounding Unit-A observations remapped to the HIRS/3 resolution, are used to retrieve the temperature profile, moisture profile, surface skin temperature, total atmospheric ozone and microwave surface emissivity, and so on. ATOVS profile retrieval results are evaluated by root-mean-square differences with respect to radiosonde observation profiles. The accuracy of the retrieval is about 2.0 K for the temperature at 1-km vertical resolution and 3.0–6.0 K for the dewpoint temperature at 2-km vertical resolution in this study. The IAPP is now available to users worldwide for processing the real-time ATOVS data.
Abstract
The International Advanced Television and Infrared Observation Satellite Operational Vertical Sounder (ATOVS) Processing Package (IAPP) has been developed to retrieve the atmospheric temperature profile, moisture profile, atmospheric total ozone, and other parameters in both clear and cloudy atmospheres from the ATOVS measurements. The algorithm that retrieves these parameters contains four steps: 1) cloud detection and removal, 2) bias adjustment for ATOVS measurements, 3) regression retrieval processes, and 4) a nonlinear iterative physical retrieval. Nine (3 × 3) adjacent High-Resolution Infrared Sounder (HIRS)/3 spot observations, together with Advanced Microwave Sounding Unit-A observations remapped to the HIRS/3 resolution, are used to retrieve the temperature profile, moisture profile, surface skin temperature, total atmospheric ozone and microwave surface emissivity, and so on. ATOVS profile retrieval results are evaluated by root-mean-square differences with respect to radiosonde observation profiles. The accuracy of the retrieval is about 2.0 K for the temperature at 1-km vertical resolution and 3.0–6.0 K for the dewpoint temperature at 2-km vertical resolution in this study. The IAPP is now available to users worldwide for processing the real-time ATOVS data.
Abstract
Between 2100 UTC 11 February 2003 and 0200 UTC 12 February 2003, a line of thunderstorms passed swiftly through parts of eastern Iowa and into north-central Illinois. Although this storm somewhat resembled a warm season, line-type mesoscale convective system, it was unique in that the thunderstorm winds exceeded the severe criterion (50 kt; 25.7 m s−1) during a snowburst. While the parent snowband deposited only 4 cm of snow, it did so in a short period and created a treacherous driving situation because of the ensuing near-whiteout conditions caused by strong winds that reached the National Weather Service severe criteria, as the line moved across central Illinois. Such storms in the cold season rarely occur and are largely undocumented; the present work seeks to fill this void in the existing literature.
While this system superficially resembled a more traditional warm season squall line, deeper inspection revealed a precipitation band that failed to conform to that paradigm. Radar analysis failed to resolve any of the necessary warm season signatures, as maximum reflectivities of only 40–45 dBZ reached no higher than 3.7 km above ground level. The result was low-topped convection in a highly sheared environment. Moreover, winds in excess of 50 kt (25.7 m s−1) occurred earlier in the day without thunderstorm activity, upstream of the eventual severe thundersnow location. Perhaps of greatest importance is the fact that the winds in excess of the severe criterion were more the result of boundary layer mixing, and largely coincident with the parent convective line. This event was a case of forced convection, dynamically linked to its parent cold front via persistent frontogenesis and the convective instability associated with it; winds sufficient for a severe thunderstorm warning, while influenced by convection, resulted from high momentum mixing downward through a dry-adiabatic layer.
Abstract
Between 2100 UTC 11 February 2003 and 0200 UTC 12 February 2003, a line of thunderstorms passed swiftly through parts of eastern Iowa and into north-central Illinois. Although this storm somewhat resembled a warm season, line-type mesoscale convective system, it was unique in that the thunderstorm winds exceeded the severe criterion (50 kt; 25.7 m s−1) during a snowburst. While the parent snowband deposited only 4 cm of snow, it did so in a short period and created a treacherous driving situation because of the ensuing near-whiteout conditions caused by strong winds that reached the National Weather Service severe criteria, as the line moved across central Illinois. Such storms in the cold season rarely occur and are largely undocumented; the present work seeks to fill this void in the existing literature.
While this system superficially resembled a more traditional warm season squall line, deeper inspection revealed a precipitation band that failed to conform to that paradigm. Radar analysis failed to resolve any of the necessary warm season signatures, as maximum reflectivities of only 40–45 dBZ reached no higher than 3.7 km above ground level. The result was low-topped convection in a highly sheared environment. Moreover, winds in excess of 50 kt (25.7 m s−1) occurred earlier in the day without thunderstorm activity, upstream of the eventual severe thundersnow location. Perhaps of greatest importance is the fact that the winds in excess of the severe criterion were more the result of boundary layer mixing, and largely coincident with the parent convective line. This event was a case of forced convection, dynamically linked to its parent cold front via persistent frontogenesis and the convective instability associated with it; winds sufficient for a severe thunderstorm warning, while influenced by convection, resulted from high momentum mixing downward through a dry-adiabatic layer.
Abstract
Single-Doppler radar along with damage observations are examined to investigate the structural evolution of vortices observed within the 29 June 1998 derecho event that propagated through southeastern Iowa into central and eastern Illinois. A total of 13 meso-γ-scale vortices observed primarily at low levels (0–3 km AGL) along the leading edge of the convective system were detected by the Weather Surveillance Radar-1988 Doppler (WSR-88D) radars at Davenport, Iowa, and Lincoln, Illinois. All but one of the vortices formed after the system evolved into a bow echo. Ten of the vortices formed north of the apex while three formed south of the apex. Seven of the vortices produced tornadoes that created F0–F1 surface damage. None of the vortices exhibited appreciable upscale growth. Careful analysis of the radar data suggests that it may be possible to discern between the tornadic and nontornadic vortices. The tornadic vortices tended to be stronger, longer-lived, and deeper than their nontornadic counterparts. The forecasting implications of these findings are discussed.
Single-Doppler radar observations documenting the evolution of midlevel (3–7 km AGL) “bookend” vortices associated with two embedded bow echoes are also presented. The first pair of midlevel vortices formed approximately 20 min after the time that the larger-scale convective system began its transition into a bow echo, had a lifetime of about 30 min, and was observed north of the primary bow apex. A second embedded bow echo formed approximately 20 min after the first, again north of the primary bow apex. The cyclonic member of this second embedded bow echo grew upscale and eventually became the dominant northern line-end vortex of the convective system. There appears to be no significant relationship or interaction between the low-level and midlevel vortices observed with this case.
Abstract
Single-Doppler radar along with damage observations are examined to investigate the structural evolution of vortices observed within the 29 June 1998 derecho event that propagated through southeastern Iowa into central and eastern Illinois. A total of 13 meso-γ-scale vortices observed primarily at low levels (0–3 km AGL) along the leading edge of the convective system were detected by the Weather Surveillance Radar-1988 Doppler (WSR-88D) radars at Davenport, Iowa, and Lincoln, Illinois. All but one of the vortices formed after the system evolved into a bow echo. Ten of the vortices formed north of the apex while three formed south of the apex. Seven of the vortices produced tornadoes that created F0–F1 surface damage. None of the vortices exhibited appreciable upscale growth. Careful analysis of the radar data suggests that it may be possible to discern between the tornadic and nontornadic vortices. The tornadic vortices tended to be stronger, longer-lived, and deeper than their nontornadic counterparts. The forecasting implications of these findings are discussed.
Single-Doppler radar observations documenting the evolution of midlevel (3–7 km AGL) “bookend” vortices associated with two embedded bow echoes are also presented. The first pair of midlevel vortices formed approximately 20 min after the time that the larger-scale convective system began its transition into a bow echo, had a lifetime of about 30 min, and was observed north of the primary bow apex. A second embedded bow echo formed approximately 20 min after the first, again north of the primary bow apex. The cyclonic member of this second embedded bow echo grew upscale and eventually became the dominant northern line-end vortex of the convective system. There appears to be no significant relationship or interaction between the low-level and midlevel vortices observed with this case.
Abstract
Seasat-A scatterometer system (SASS) measurements of wind speed and direction and GOES-2 satellite measurements of cloud motion directions were used to analyze the surface wind field over part of the northern Pacific Ocean for 17 July and 3 October 1978. Surface pressure fields were computed from the nondivergent SASS-derived wind velocity fields using the balance equation and were compared to the National Meteorological Center surface pressure fields. Agreement between the balanced pressure-height fields and National Meteorological Center pressure fields was good. The linear correlation coefficient between the two fields was 0.91 for 17 July, and 0.84 for 3 October 1978. These results indicate that the surface wind and pressure fields of the global oceans (excluding a narrow equatorial zone where the balance equation is invalid) can be determined with acceptable accuracy by using satellite measurements exclusively.
Abstract
Seasat-A scatterometer system (SASS) measurements of wind speed and direction and GOES-2 satellite measurements of cloud motion directions were used to analyze the surface wind field over part of the northern Pacific Ocean for 17 July and 3 October 1978. Surface pressure fields were computed from the nondivergent SASS-derived wind velocity fields using the balance equation and were compared to the National Meteorological Center surface pressure fields. Agreement between the balanced pressure-height fields and National Meteorological Center pressure fields was good. The linear correlation coefficient between the two fields was 0.91 for 17 July, and 0.84 for 3 October 1978. These results indicate that the surface wind and pressure fields of the global oceans (excluding a narrow equatorial zone where the balance equation is invalid) can be determined with acceptable accuracy by using satellite measurements exclusively.
Abstract
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Abstract
Drought indices are often used for monitoring interannual variability in macroscale hydrology. However, the diversity of drought indices raises several issues: 1) which indices perform best and where; 2) does the incorporation of potential evapotranspiration (PET) in indices strengthen relationships, and how sensitive is the choice of PET methods to such results; 3) what additional value is added by using higher-spatial-resolution gridded climate layers; and 4) how have observed relationships changed through time. Standardized precipitation index, standardized precipitation evapotranspiration index (SPEI), Palmer drought severity index, and water balance runoff (WBR) model output were correlated to water-year runoff for 21 unregulated drainage basins in the Pacific Northwest of the United States. SPEI and WBR with time scales encompassing the primary precipitation season maximized the explained variance in water-year runoff in most basins. Slightly stronger correlations were found using PET estimates from the Penman–Monteith method over the Thornthwaite method, particularly for time periods that incorporated the spring and summer months in basins that receive appreciable precipitation during the growing season. Indices computed using high-resolution climate surfaces explained over 10% more variability than metrics derived from coarser-resolution datasets. Increased correlation in the latter half of the study period was partially attributable to increased streamflow variability in recent decades as well as to improved climate data quality across the interior mountain watersheds.
Abstract
Drought indices are often used for monitoring interannual variability in macroscale hydrology. However, the diversity of drought indices raises several issues: 1) which indices perform best and where; 2) does the incorporation of potential evapotranspiration (PET) in indices strengthen relationships, and how sensitive is the choice of PET methods to such results; 3) what additional value is added by using higher-spatial-resolution gridded climate layers; and 4) how have observed relationships changed through time. Standardized precipitation index, standardized precipitation evapotranspiration index (SPEI), Palmer drought severity index, and water balance runoff (WBR) model output were correlated to water-year runoff for 21 unregulated drainage basins in the Pacific Northwest of the United States. SPEI and WBR with time scales encompassing the primary precipitation season maximized the explained variance in water-year runoff in most basins. Slightly stronger correlations were found using PET estimates from the Penman–Monteith method over the Thornthwaite method, particularly for time periods that incorporated the spring and summer months in basins that receive appreciable precipitation during the growing season. Indices computed using high-resolution climate surfaces explained over 10% more variability than metrics derived from coarser-resolution datasets. Increased correlation in the latter half of the study period was partially attributable to increased streamflow variability in recent decades as well as to improved climate data quality across the interior mountain watersheds.
Abstract
Postevent damage surveys conducted during the Bow Echo and Mesoscale Convective Vortex Experiment demonstrate that the severe thunderstorm wind reports in Storm Data served as a poor characterization of the actual scope and magnitude of the surveyed damage. Contrasting examples are presented in which a few reports grossly underrepresented a significant event (in terms of property damage and actual areal coverage of damage), while a large number of reports overrepresented a relatively less significant event. Explanations and further discussion of this problem are provided, as are some of the implications, which may include a skewed understanding of how and when systems of thunderstorms cause damage. A number of recommendations pertaining to severe wind reporting are offered.
Abstract
Postevent damage surveys conducted during the Bow Echo and Mesoscale Convective Vortex Experiment demonstrate that the severe thunderstorm wind reports in Storm Data served as a poor characterization of the actual scope and magnitude of the surveyed damage. Contrasting examples are presented in which a few reports grossly underrepresented a significant event (in terms of property damage and actual areal coverage of damage), while a large number of reports overrepresented a relatively less significant event. Explanations and further discussion of this problem are provided, as are some of the implications, which may include a skewed understanding of how and when systems of thunderstorms cause damage. A number of recommendations pertaining to severe wind reporting are offered.
Estimation of Near-Real-Time Outgoing Longwave Radiation from Cross-Track Infrared Sounder (CrIS) Radiance MeasurementsAbstract
This study describes the algorithm for deriving near-real-time outgoing longwave radiation (OLR) from Cross-Track Infrared Sounder (CrIS) hyperspectral infrared sounder radiance measurements. The estimation of OLR on a near-real-time basis provides a unique perspective for studying the variability of Earth’s current atmospheric radiation budget. CrIS-derived OLR values are estimated as a weighted linear combination of CrIS-adjusted “pseudochannel” radiances. The algorithm uses the Atmospheric Infrared Sounder (AIRS) as the transfer instrument, and a least squares regression algorithm is applied to generate two sets of regression coefficients. The first set of regression coefficients is derived from collocated Clouds and the Earth’s Radiant Energy System (CERES) OLR on Aqua and pseudochannel radiances calculated from AIRS radiances. The second set of coefficients is derived to adjust the CrIS pseudochannel radiance to account for the differences in pseudochannel radiances between AIRS and CrIS. The CrIS-derived OLR is then validated by using a limited set of available CERES SNPP OLR observations over 1° × 1° global grids, as well as monthly OLR mean and interannual differences against CERES OLR datasets from SNPP and Aqua. The results show that the bias of global CrIS OLR estimation is within ±2 W m−2 and that the standard deviation is within 5 W m−2 for all conditions, and ±1 and 3 W m−2 for homogeneous scenes. The interannual CrIS-derived OLR differences agree well with Aqua CERES interannual OLR differences on a 1° × 1° spatial scale, with only a small drift of the global mean of these two datasets of around 0.004 W m−2.
Abstract
This study describes the algorithm for deriving near-real-time outgoing longwave radiation (OLR) from Cross-Track Infrared Sounder (CrIS) hyperspectral infrared sounder radiance measurements. The estimation of OLR on a near-real-time basis provides a unique perspective for studying the variability of Earth’s current atmospheric radiation budget. CrIS-derived OLR values are estimated as a weighted linear combination of CrIS-adjusted “pseudochannel” radiances. The algorithm uses the Atmospheric Infrared Sounder (AIRS) as the transfer instrument, and a least squares regression algorithm is applied to generate two sets of regression coefficients. The first set of regression coefficients is derived from collocated Clouds and the Earth’s Radiant Energy System (CERES) OLR on Aqua and pseudochannel radiances calculated from AIRS radiances. The second set of coefficients is derived to adjust the CrIS pseudochannel radiance to account for the differences in pseudochannel radiances between AIRS and CrIS. The CrIS-derived OLR is then validated by using a limited set of available CERES SNPP OLR observations over 1° × 1° global grids, as well as monthly OLR mean and interannual differences against CERES OLR datasets from SNPP and Aqua. The results show that the bias of global CrIS OLR estimation is within ±2 W m−2 and that the standard deviation is within 5 W m−2 for all conditions, and ±1 and 3 W m−2 for homogeneous scenes. The interannual CrIS-derived OLR differences agree well with Aqua CERES interannual OLR differences on a 1° × 1° spatial scale, with only a small drift of the global mean of these two datasets of around 0.004 W m−2.
