Search Results
Abstract
In contrast to short and extended range forecasts, predictions for periods beyond 5 days use time-averaged, midtropospheric height fields as their primary guidance. As time ranges are increased to 3O- and 90-day outlooks, guidance increasingly relies on statistical techniques using autocorrelation fields rather than numerical weather prediction (NWP) products as the primary prediction tool.
The basis for the medium-range 6- to 10-day forecast is a mean 500 mb height and anomaly field for the forecast period, derived from a mix of output from two different numerical models, with some statistical and subjective modification added if desired.
The monthly or 30-day outlook is based on a subjectively constructed mean 700 mb prognostic map based on available NWP mean height and anomaly fields out to 10 days, the appropriate 700 mb 1-month lag auto-correlation field, and subjective use of teleconnection and empirical orthogonal function patterns for consistency.
A quantitative midtropospheric height and anomaly map is not constructed for the seasonal (90-day) outlook, but statistically significant height indications are obtained from a series of seasonal 700 mb lag autocorrelation fields going back as far as 2 1/1 years. Numerical weather prediction products do not enter into the seasonal forecast, but boundary forcing by sea surface temperature anomalies, particularly in the Pacific, is considered during the seasons these factors have been shown to have a significant effect on the mean circulation. Extensive use is made of teleconnections to obtain a consistent overall qualitative concept of the expected pattern.
Mean surface temperature and precipitation anomalies expressed either in terms of probabilities or categories are the main forecast products. The skill varies regionally and seasonally, is considerably less than for short-range forecasts, and declines slowly with increasing length of the forecast period.
Abstract
In contrast to short and extended range forecasts, predictions for periods beyond 5 days use time-averaged, midtropospheric height fields as their primary guidance. As time ranges are increased to 3O- and 90-day outlooks, guidance increasingly relies on statistical techniques using autocorrelation fields rather than numerical weather prediction (NWP) products as the primary prediction tool.
The basis for the medium-range 6- to 10-day forecast is a mean 500 mb height and anomaly field for the forecast period, derived from a mix of output from two different numerical models, with some statistical and subjective modification added if desired.
The monthly or 30-day outlook is based on a subjectively constructed mean 700 mb prognostic map based on available NWP mean height and anomaly fields out to 10 days, the appropriate 700 mb 1-month lag auto-correlation field, and subjective use of teleconnection and empirical orthogonal function patterns for consistency.
A quantitative midtropospheric height and anomaly map is not constructed for the seasonal (90-day) outlook, but statistically significant height indications are obtained from a series of seasonal 700 mb lag autocorrelation fields going back as far as 2 1/1 years. Numerical weather prediction products do not enter into the seasonal forecast, but boundary forcing by sea surface temperature anomalies, particularly in the Pacific, is considered during the seasons these factors have been shown to have a significant effect on the mean circulation. Extensive use is made of teleconnections to obtain a consistent overall qualitative concept of the expected pattern.
Mean surface temperature and precipitation anomalies expressed either in terms of probabilities or categories are the main forecast products. The skill varies regionally and seasonally, is considerably less than for short-range forecasts, and declines slowly with increasing length of the forecast period.
Abstract
Aircraft-based observations (ABOs) are an important component of the global observation system. Observations of pressure, temperature, and wind are obtained from thousands of routine commercial flights daily via the Aircraft Meteorological Data Relay (AMDAR) program, while a subset of approximately 145 aircraft globally (and 135 within the conterminous United States) also produces observations of water vapor from the Water Vapor Sensing System–II (WVSS–II). Aircraft equipped with WVSS–II provide the basic parameters as radiosonde observations throughout most of the troposphere, often at higher temporal and spatial frequency. Since these aircraft are operated according to the demands of passenger and cargo, the availability of aircraft profiles varies significantly in space and time, with more profiles during daytime and early evening than overnight, more profiles on weekdays than weekends, and more during the summer months. The number of available profiles was significantly impacted by reductions in travel during the COVID-19 pandemic but has recovered substantially. The potential for aircraft profiles to support the operational radiosonde network is explored, including the effect of various spatial and temporal matching criteria. Radiosonde launches at 0000 UTC that are well aligned with aircraft profiles are found across the conterminous United States, but well-covered 1200 UTC launches are strongly biased to the east. ABO coverage of asynoptic launch times is also explored. The busiest sites usually have multiple compatible aircraft profiles at both synoptic and asynoptic times. This redundancy lends robustness to the observation network and enables forecasters to monitor atmospheric evolution more continuously throughout the day.
Significance Statement
Some commercial aircraft make the same observations as weather balloons, but there is not a good record of how frequently these observations are made at specific locations. This paper does a census of where the airplane profile observations are most likely to be found and shows where they are duplicating weather balloon observations and where they are filling in the gaps in the weather balloon network.
Abstract
Aircraft-based observations (ABOs) are an important component of the global observation system. Observations of pressure, temperature, and wind are obtained from thousands of routine commercial flights daily via the Aircraft Meteorological Data Relay (AMDAR) program, while a subset of approximately 145 aircraft globally (and 135 within the conterminous United States) also produces observations of water vapor from the Water Vapor Sensing System–II (WVSS–II). Aircraft equipped with WVSS–II provide the basic parameters as radiosonde observations throughout most of the troposphere, often at higher temporal and spatial frequency. Since these aircraft are operated according to the demands of passenger and cargo, the availability of aircraft profiles varies significantly in space and time, with more profiles during daytime and early evening than overnight, more profiles on weekdays than weekends, and more during the summer months. The number of available profiles was significantly impacted by reductions in travel during the COVID-19 pandemic but has recovered substantially. The potential for aircraft profiles to support the operational radiosonde network is explored, including the effect of various spatial and temporal matching criteria. Radiosonde launches at 0000 UTC that are well aligned with aircraft profiles are found across the conterminous United States, but well-covered 1200 UTC launches are strongly biased to the east. ABO coverage of asynoptic launch times is also explored. The busiest sites usually have multiple compatible aircraft profiles at both synoptic and asynoptic times. This redundancy lends robustness to the observation network and enables forecasters to monitor atmospheric evolution more continuously throughout the day.
Significance Statement
Some commercial aircraft make the same observations as weather balloons, but there is not a good record of how frequently these observations are made at specific locations. This paper does a census of where the airplane profile observations are most likely to be found and shows where they are duplicating weather balloon observations and where they are filling in the gaps in the weather balloon network.
