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- Author or Editor: Patrick J. Michaels x
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Abstract
Multivariate analyses of acreage abandonment patterns in the U.S. Great Plains winter wheat region indicate that the major mode of variation is an in-phase oscillation confined to the western half of the overall area, which is also the area with lowest average yields. This is one of the more agroclimatically marginal environments in the United States, with wide interannual fluctuations in both climate and profitability.
We developed a multiple regression model to determine the relative roles of weather and expected price in the decision not to harvest. The overall model explained 77% of the spatial and temporal variation in abandonment. The 36.5% of the non-spatial variation was explained by two simple transformations of climatic data from three monthly aggregates—September–October, November–February and March–April. Price factors, expressed as indexed future delivery quotations,were barely significant, with only between 3 and 5% of the non-spatial variation explained, depending upon the model.
The model was based upon weather, climate and price data from 1932 through 1975. It was tested by sequentially withholding three-year blocks of data, and using the respecified regression coefficients, along with observed weather and price, to estimate abandonment in the withheld years. Error analyses indicate no loss of model fidelity in the test mode. Also, prediction errors in the 1970–75 period, characterized by widely fluctuating prices, were not different from those in the rest of the model.
The overall results suggest that the perceived quality of the crop, as influenced by weather, is a much more important determinant of the abandonment decision than are expected returns based upon price considerations.
Abstract
Multivariate analyses of acreage abandonment patterns in the U.S. Great Plains winter wheat region indicate that the major mode of variation is an in-phase oscillation confined to the western half of the overall area, which is also the area with lowest average yields. This is one of the more agroclimatically marginal environments in the United States, with wide interannual fluctuations in both climate and profitability.
We developed a multiple regression model to determine the relative roles of weather and expected price in the decision not to harvest. The overall model explained 77% of the spatial and temporal variation in abandonment. The 36.5% of the non-spatial variation was explained by two simple transformations of climatic data from three monthly aggregates—September–October, November–February and March–April. Price factors, expressed as indexed future delivery quotations,were barely significant, with only between 3 and 5% of the non-spatial variation explained, depending upon the model.
The model was based upon weather, climate and price data from 1932 through 1975. It was tested by sequentially withholding three-year blocks of data, and using the respecified regression coefficients, along with observed weather and price, to estimate abandonment in the withheld years. Error analyses indicate no loss of model fidelity in the test mode. Also, prediction errors in the 1970–75 period, characterized by widely fluctuating prices, were not different from those in the rest of the model.
The overall results suggest that the perceived quality of the crop, as influenced by weather, is a much more important determinant of the abandonment decision than are expected returns based upon price considerations.
Abstract
GOES imagery from 7 September 1981 shows five tropical disturbances in various stages of development. While the photo appears to indicate that they may be recurving under the influence of a persistent weakness in the subtropical ridge, analyses show that two were probably deflected northeastward by separate short waves in the upper troposphere. A slight change in amplitude or position of those waves or of the ridge could have resulted in unusually frequent activity on the U.S. Atlantic Coast.
Abstract
GOES imagery from 7 September 1981 shows five tropical disturbances in various stages of development. While the photo appears to indicate that they may be recurving under the influence of a persistent weakness in the subtropical ridge, analyses show that two were probably deflected northeastward by separate short waves in the upper troposphere. A slight change in amplitude or position of those waves or of the ridge could have resulted in unusually frequent activity on the U.S. Atlantic Coast.
One popular and apocalyptic vision of the world influenced by increasing concentrations of infrared-absorbing trace gases is that of ecological disaster brought about by rapidly rising temperatures, sea level, and evaporation rates. This vision developed from a suite of climate models that have since considerably changed in both their dynamics and their estimates of prospective warming. Observed temperatures indicate that much more warming should already have taken place than predicted by earlier models in the Northern Hemisphere, and that night, rather than day, readings in that hemisphere show a relative warming. A high-latitude polar-night warming or a general night warming could be either benign or beneficial. A large number of plant species show both increased growth and greater water-use efficiency under enhanced carbon dioxide.
An extensive body of evidence now indicates that anthropogenerated sulfate emissions are mitigating some of the warming, and that increased cloudiness as a result of these emissions will further enhance night, rather than day, warming. The sulfate emissions, though, are not sufficient to explain all of the night warming. However, the sensitivity of climate to anthropogenerated aerosols, and the general lack of previously predicted warming, could drastically alter the debate on global warming in favor of less expensive policies.
One popular and apocalyptic vision of the world influenced by increasing concentrations of infrared-absorbing trace gases is that of ecological disaster brought about by rapidly rising temperatures, sea level, and evaporation rates. This vision developed from a suite of climate models that have since considerably changed in both their dynamics and their estimates of prospective warming. Observed temperatures indicate that much more warming should already have taken place than predicted by earlier models in the Northern Hemisphere, and that night, rather than day, readings in that hemisphere show a relative warming. A high-latitude polar-night warming or a general night warming could be either benign or beneficial. A large number of plant species show both increased growth and greater water-use efficiency under enhanced carbon dioxide.
An extensive body of evidence now indicates that anthropogenerated sulfate emissions are mitigating some of the warming, and that increased cloudiness as a result of these emissions will further enhance night, rather than day, warming. The sulfate emissions, though, are not sufficient to explain all of the night warming. However, the sensitivity of climate to anthropogenerated aerosols, and the general lack of previously predicted warming, could drastically alter the debate on global warming in favor of less expensive policies.
Abstract
An orthogonal principal component analysis of National Climatic Center summer thunderstorm frequency data over Virginia revealed five statistically significant modes of variation. In some, power was spread statewide, while in others it was concentrated over a few small regions. A similar analysis was performed on the NCAR record of monthly 500 mb heights over North America, and four significant height patterns were determined.
Multiple regression was used to relate the individual thunderstorm components to the upper-air patterns. The fit of each time series of the first four thunderstorm components by the 500 mb patterns was statistically significant, with approximately one-third of the variance of the thunderstorm pattern explained. A subsequent canonical correlation revealed one significant multivariate relationship.
The results provide statistically significant evidence for the linkage between macroscale flow patterns and mesoscale convective storms.
Abstract
An orthogonal principal component analysis of National Climatic Center summer thunderstorm frequency data over Virginia revealed five statistically significant modes of variation. In some, power was spread statewide, while in others it was concentrated over a few small regions. A similar analysis was performed on the NCAR record of monthly 500 mb heights over North America, and four significant height patterns were determined.
Multiple regression was used to relate the individual thunderstorm components to the upper-air patterns. The fit of each time series of the first four thunderstorm components by the 500 mb patterns was statistically significant, with approximately one-third of the variance of the thunderstorm pattern explained. A subsequent canonical correlation revealed one significant multivariate relationship.
The results provide statistically significant evidence for the linkage between macroscale flow patterns and mesoscale convective storms.
Abstract
Using permafrost boreholes, Lachenbruch and Marshall recently reported evidence for a 2°–4°C warming in North Alaska occurring at some undetermined time during the last century. Popular accounts suggest their findings are evidence for anthropogenic warming caused by trace gases. Analyses of North Alaskan 1000-500 mb thickness onwards back to 1948 indicate that the warming was prior to that date. Relatively sparse thermometric data for the early twentieth century from Jones et al. are too noisy to support any trend since the data record begins in 1910, or to apply to any subperiod of climatic significance. Any warming detected from the permafrost record therefore occurred before the major emissions of thermally active trace gases.
Abstract
Using permafrost boreholes, Lachenbruch and Marshall recently reported evidence for a 2°–4°C warming in North Alaska occurring at some undetermined time during the last century. Popular accounts suggest their findings are evidence for anthropogenic warming caused by trace gases. Analyses of North Alaskan 1000-500 mb thickness onwards back to 1948 indicate that the warming was prior to that date. Relatively sparse thermometric data for the early twentieth century from Jones et al. are too noisy to support any trend since the data record begins in 1910, or to apply to any subperiod of climatic significance. Any warming detected from the permafrost record therefore occurred before the major emissions of thermally active trace gases.
Abstract
In a simulation of enhanced tropical cyclones in a warmer world, Knutson and Tuleya make several assumptions that are not borne out in the real world. They include an unrealistically large carbon dioxide growth rate, an overly strong relationship between sea surface temperature and hurricane intensity, and the use of a mesoscale model that has shown little to no useful skill in predicting current-day hurricane intensity. After accounting for these inaccuracies, a detectable increase in Atlantic hurricane intensity in response to growing atmospheric greenhouse gas levels during this century becomes unlikely.
Abstract
In a simulation of enhanced tropical cyclones in a warmer world, Knutson and Tuleya make several assumptions that are not borne out in the real world. They include an unrealistically large carbon dioxide growth rate, an overly strong relationship between sea surface temperature and hurricane intensity, and the use of a mesoscale model that has shown little to no useful skill in predicting current-day hurricane intensity. After accounting for these inaccuracies, a detectable increase in Atlantic hurricane intensity in response to growing atmospheric greenhouse gas levels during this century becomes unlikely.
Abstract
In an attempt to produce an objective climatology of peninsular Florida thunderstorms that does not suffer from observer bias, we composited 9088 hours of high-resolution manually digitized radar (MDR) data and 28 days of daytime satellite imagery. Both indicated maximum activity over the southwestern corner of the peninsula. Radar shows much higher frequencies than are found in other studies, but this is due in part to the method of data collection. We then decomposed the MDR data into Principal Components (PC) to isolate independent spatial and temporal patterns. The most important pattern had a strong diurnal component that was very congruent with coastline geography. Additional important PCs generate the most likely daily regime.
A temporal analysis of the daily march of the radar PC composites over the area of highest activity indicates two discrete diurnal maxima. Over southwestern south Florida (near Flamingo), activity peaks sharply around 2000 UTC. There is another discrete peak in activity approximately 200 km to the northwest two hours later.
Satellite composites also demonstrated that deep cumulonimbus activity over south Florida on undisturbed summer days is strongly focused by the peninsula.
In a statistical analysis at the synoptic scale, interdiurnal variability in the radar PCs is more related to variation at the 850 mb level than variation at the surface.
Abstract
In an attempt to produce an objective climatology of peninsular Florida thunderstorms that does not suffer from observer bias, we composited 9088 hours of high-resolution manually digitized radar (MDR) data and 28 days of daytime satellite imagery. Both indicated maximum activity over the southwestern corner of the peninsula. Radar shows much higher frequencies than are found in other studies, but this is due in part to the method of data collection. We then decomposed the MDR data into Principal Components (PC) to isolate independent spatial and temporal patterns. The most important pattern had a strong diurnal component that was very congruent with coastline geography. Additional important PCs generate the most likely daily regime.
A temporal analysis of the daily march of the radar PC composites over the area of highest activity indicates two discrete diurnal maxima. Over southwestern south Florida (near Flamingo), activity peaks sharply around 2000 UTC. There is another discrete peak in activity approximately 200 km to the northwest two hours later.
Satellite composites also demonstrated that deep cumulonimbus activity over south Florida on undisturbed summer days is strongly focused by the peninsula.
In a statistical analysis at the synoptic scale, interdiurnal variability in the radar PCs is more related to variation at the 850 mb level than variation at the surface.
Abstract
In situ data collected within a weakly tornadic, high-precipitation supercell occurring on 23 May 2007 near Perryton, Texas, are presented. Data were collected using a recently developed fleet of 22 durable, rapidly deployable probes dubbed “StickNet” as well as four mobile mesonet probes. Kinematic and thermodynamic observations of boundaries within the supercell are described in tandem with an analysis of data from the Shared Mobile Atmospheric Research and Teaching Radar.
Observations within the rear-flank downdraft of the storm exhibit large deficits of both virtual potential temperature and equivalent potential temperature, with a secondary rear-flank downdraft gust front trailing the mesocyclone. A primarily thermodynamic boundary resided across the forward-flank reflectivity gradient of the supercell. This boundary is characterized by small deficits in virtual potential temperature coupled with positive perturbations of equivalent potential temperature. The opposing thermodynamic perturbations appear to be representative of modified storm inflow, with a flux of water vapor responsible for the positive perturbations of the equivalent potential temperature. Air parcels exhibiting negative perturbations of virtual potential temperature and positive perturbations of equivalent potential temperature have the ability to be a source of both baroclinically generated streamwise horizontal vorticity and greater potential buoyancy if ingested by the low-level mesocyclone.
Abstract
In situ data collected within a weakly tornadic, high-precipitation supercell occurring on 23 May 2007 near Perryton, Texas, are presented. Data were collected using a recently developed fleet of 22 durable, rapidly deployable probes dubbed “StickNet” as well as four mobile mesonet probes. Kinematic and thermodynamic observations of boundaries within the supercell are described in tandem with an analysis of data from the Shared Mobile Atmospheric Research and Teaching Radar.
Observations within the rear-flank downdraft of the storm exhibit large deficits of both virtual potential temperature and equivalent potential temperature, with a secondary rear-flank downdraft gust front trailing the mesocyclone. A primarily thermodynamic boundary resided across the forward-flank reflectivity gradient of the supercell. This boundary is characterized by small deficits in virtual potential temperature coupled with positive perturbations of equivalent potential temperature. The opposing thermodynamic perturbations appear to be representative of modified storm inflow, with a flux of water vapor responsible for the positive perturbations of the equivalent potential temperature. Air parcels exhibiting negative perturbations of virtual potential temperature and positive perturbations of equivalent potential temperature have the ability to be a source of both baroclinically generated streamwise horizontal vorticity and greater potential buoyancy if ingested by the low-level mesocyclone.
Abstract
Unique observations of the interaction and likely merger of two cyclonic tornadoes are documented. One of the tornadoes involved in the interaction was the enhanced Fujita scale (EF5) El Reno–Piedmont, Oklahoma, tornado from 24 May 2011 and the other was a previously undocumented tornado. Data from three S-band radars: Twin Lakes, Oklahoma (KTLX); Norman, Oklahoma (KOUN); and the multifunction phased-array radar (MPAR), are used to detail the formation of the second tornado, which occurred to the northwest of the original tornado in an area of strong radial convergence. Radar data and isosurfaces of azimuthal shear provide evidence that both tornadoes formed within an elongated area of mesocyclone-scale cyclonic rotation. The path taken by the primary tornado and the formation location of the second tornado are different from previous observations of simultaneous cyclonic tornadoes, which have been most often observed in the cyclic tornadogenesis process. The merger of the two tornadoes occurred during the sampling period of a mobile phased-array radar—the Mobile Weather Radar, 2005 X-Band, Phased Array (MWR-05XP). MWR-05XP electronic scanning in elevation allowed for the merger process to be examined up to 4 km above radar level every 11 s. The tornadic vortex signatures (TVSs) associated with the tornadoes traveled around each other in a counterclockwise direction then merged in a helical manner up through storm midlevels. Upon merging, both the estimated intensity and size of the TVS associated with the resulting tornado increased dramatically. Similarities between the merger observed in this case and in previous cases also are discussed.
Abstract
Unique observations of the interaction and likely merger of two cyclonic tornadoes are documented. One of the tornadoes involved in the interaction was the enhanced Fujita scale (EF5) El Reno–Piedmont, Oklahoma, tornado from 24 May 2011 and the other was a previously undocumented tornado. Data from three S-band radars: Twin Lakes, Oklahoma (KTLX); Norman, Oklahoma (KOUN); and the multifunction phased-array radar (MPAR), are used to detail the formation of the second tornado, which occurred to the northwest of the original tornado in an area of strong radial convergence. Radar data and isosurfaces of azimuthal shear provide evidence that both tornadoes formed within an elongated area of mesocyclone-scale cyclonic rotation. The path taken by the primary tornado and the formation location of the second tornado are different from previous observations of simultaneous cyclonic tornadoes, which have been most often observed in the cyclic tornadogenesis process. The merger of the two tornadoes occurred during the sampling period of a mobile phased-array radar—the Mobile Weather Radar, 2005 X-Band, Phased Array (MWR-05XP). MWR-05XP electronic scanning in elevation allowed for the merger process to be examined up to 4 km above radar level every 11 s. The tornadic vortex signatures (TVSs) associated with the tornadoes traveled around each other in a counterclockwise direction then merged in a helical manner up through storm midlevels. Upon merging, both the estimated intensity and size of the TVS associated with the resulting tornado increased dramatically. Similarities between the merger observed in this case and in previous cases also are discussed.
Abstract
This report describes sampling and error characteristics of self-siphoning rain gauges used on moored buoys designed and assembled at NOAA's Pacific Marine Environmental Laboratory (PMEL) for deployment in the tropical Pacific and Atlantic Oceans in support of climate studies. Self-siphoning rain gauges were chosen for use on these buoys because they can be calibrated at PMEL before and after deployment. The rainfall data are recorded at 1-min intervals, from which daily mean rate, standard deviation, and percent time raining are calculated and telemetered to PMEL in real time. At the end of the deployment, the 1-min, internally recorded data are recovered and processed to produce 10-min rain rates.
Field data from a subset of these rain gauges are analyzed to determine data quality and noise levels. In addition, laboratory experiments are performed to assess gauge performance. The field data indicate that the noise level during periods of no rain is 0.3 mm h−1 for 1-min data, and 0.1 mm h−1 for 10-min data. The estimated error in the derived rain rates, based on the laboratory data, is 1.3 mm h−1 for 1-min data, and 0.4 mm h−1 for 10-min data. The error in the real-time daily rain rates is estimated to be at most 0.03 mm h−1. These error estimates do not take into account underestimates in accumulations due to effects of wind speed on catchment efficiency, which, though substantial, may be correctable. Estimated errors due to evaporation and sea spray, on the other hand, are found to be insignificant.
Abstract
This report describes sampling and error characteristics of self-siphoning rain gauges used on moored buoys designed and assembled at NOAA's Pacific Marine Environmental Laboratory (PMEL) for deployment in the tropical Pacific and Atlantic Oceans in support of climate studies. Self-siphoning rain gauges were chosen for use on these buoys because they can be calibrated at PMEL before and after deployment. The rainfall data are recorded at 1-min intervals, from which daily mean rate, standard deviation, and percent time raining are calculated and telemetered to PMEL in real time. At the end of the deployment, the 1-min, internally recorded data are recovered and processed to produce 10-min rain rates.
Field data from a subset of these rain gauges are analyzed to determine data quality and noise levels. In addition, laboratory experiments are performed to assess gauge performance. The field data indicate that the noise level during periods of no rain is 0.3 mm h−1 for 1-min data, and 0.1 mm h−1 for 10-min data. The estimated error in the derived rain rates, based on the laboratory data, is 1.3 mm h−1 for 1-min data, and 0.4 mm h−1 for 10-min data. The error in the real-time daily rain rates is estimated to be at most 0.03 mm h−1. These error estimates do not take into account underestimates in accumulations due to effects of wind speed on catchment efficiency, which, though substantial, may be correctable. Estimated errors due to evaporation and sea spray, on the other hand, are found to be insignificant.
