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• 1. [Article] Seasonal variations of water vapor in the tropical lower stratosphere

  Measurements of stratospheric water vapor by the Microwave Limb Sounder aboard the Upper Atmosphere Research Satellite show that in the tropical lower stratosphere, low-frequency variations are closely related ...

  Citation × Citation Citation Abstract Copy Title: Seasonal variations of water vapor in the tropical lower stratosphere Author: Harwood, Robert S., Waters, Joe W., Holton, James R., Rosenloh, Karen H., Mote, Philip W. Measurements of stratospheric water vapor by the Microwave Limb Sounder aboard the Upper Atmosphere Research Satellite show that in the tropical lower stratosphere, low-frequency variations are closely related to the annual cycle in tropical tropopause temperatures. Tropical stratospheric air appears to retain information about the tropopause conditions it encountered for over a year as it rises through the stratosphere. We use a two-dimensional Lagrangian model to relate MLS measurements to the temperature that tropical air parcels encountered when crossing the 100 hPa surface. Title: Seasonal variations of water vapor in the tropical lower stratosphere Author: Harwood, Robert S., Waters, Joe W., Holton, James R., Rosenloh, Karen H., Mote, Philip W. Measurements of stratospheric water vapor by the Microwave Limb Sounder aboard the Upper Atmosphere Research Satellite show that in the tropical lower stratosphere, low-frequency variations are closely related to the annual cycle in tropical tropopause temperatures. Tropical stratospheric air appears to retain information about the tropopause conditions it encountered for over a year as it rises through the stratosphere. We use a two-dimensional Lagrangian model to relate MLS measurements to the temperature that tropical air parcels encountered when crossing the 100 hPa surface. Close

• 2. [Article] Intraseasonal variations of water vapor in the tropical upper troposphere and tropopause region

  We show the signature of the tropical intraseasonal oscillation (TIO) in upper tropospheric moisture and dynamical fields, roughly between 200 and 100 hPa. Relationships among these fields are examined ...

  Citation × Citation Citation Abstract Copy Title: Intraseasonal variations of water vapor in the tropical upper troposphere and tropopause region Author: Clark, Hannah L., Dunkerton, Timothy J., Mote, Philip W., Harwood, Robert S., Pumphrey, Hugh C. We show the signature of the tropical intraseasonal oscillation (TIO) in upper tropospheric moisture and dynamical fields, roughly between 200 and 100 hPa. Relationships among these fields are examined using lag-correlation analysis and using multivariate extended empirical orthogonal functions (MEEOFs), which maximize the shared explained variance among several fields for both spatial and temporal variations. The MEEOFs show that all of the fields respond to the TIO and that the TIO is the dominant factor influencing each of the fields on these timescales. Convection associated with the TIO moistens the upper troposphere up to about 150 hPa, as expected; the behavior at 100 hPa is more complex. Over the longitude range where the TIO is associated with convection, roughly 60°-180°E, 100-hPa temperature and water vapor tend to be reduced above convection on TIO timescales. East of 180°, though, the temperature and water vapor variations at 100 hPa become decoupled. The water vapor variations, like those of 200-hPa velocity potential, appear to speed up at about 180°E. Title: Intraseasonal variations of water vapor in the tropical upper troposphere and tropopause region Author: Clark, Hannah L., Dunkerton, Timothy J., Mote, Philip W., Harwood, Robert S., Pumphrey, Hugh C. We show the signature of the tropical intraseasonal oscillation (TIO) in upper tropospheric moisture and dynamical fields, roughly between 200 and 100 hPa. Relationships among these fields are examined using lag-correlation analysis and using multivariate extended empirical orthogonal functions (MEEOFs), which maximize the shared explained variance among several fields for both spatial and temporal variations. The MEEOFs show that all of the fields respond to the TIO and that the TIO is the dominant factor influencing each of the fields on these timescales. Convection associated with the TIO moistens the upper troposphere up to about 150 hPa, as expected; the behavior at 100 hPa is more complex. Over the longitude range where the TIO is associated with convection, roughly 60°-180°E, 100-hPa temperature and water vapor tend to be reduced above convection on TIO timescales. East of 180°, though, the temperature and water vapor variations at 100 hPa become decoupled. The water vapor variations, like those of 200-hPa velocity potential, appear to speed up at about 180°E. Close

• 3. [Article] Stratospheric Flow during Two Recent Winters Simulated by a Mechanistic Model

  The authors have used a spectral, primitive equation mechanistic model of the stratosphere and mesosphere to simulate observed stratospheric flow through the winters of 1991–92 and 1994–95 by forcing the ...

  Citation × Citation Citation Abstract Copy Title: Stratospheric Flow during Two Recent Winters Simulated by a Mechanistic Model Author: Stott, Peter A., Mote, Philip W., Harwood, Robert S. The authors have used a spectral, primitive equation mechanistic model of the stratosphere and mesosphere to simulate observed stratospheric flow through the winters of 1991–92 and 1994–95 by forcing the model at 100 hPa with observed geopotential height. The authors assess the model’s performance quantitatively by comparing the simulations with the United Kingdom Meteorological Office (UKMO) assimilated stratosphere– troposphere data. Time-mean, zonal-mean temperatures are generally within 5 K and winds within 5 m s⁻¹; transient features, such as wave growth, are mostly simulated well. The phase accuracy of planetary-scale waves declines with altitude and wavenumber, and the model has difficulty correctly simulating traveling anticyclones in the upper stratosphere. The authors examine the minor warming of January 1995 which was unusual in its depth and development and which the model simulated fairly well. The authors also examine the minor warming of January 1992, which the model missed, and a major warming in February 1992 that occurred in the model but not in the observations. Title: Stratospheric Flow during Two Recent Winters Simulated by a Mechanistic Model Author: Stott, Peter A., Mote, Philip W., Harwood, Robert S. The authors have used a spectral, primitive equation mechanistic model of the stratosphere and mesosphere to simulate observed stratospheric flow through the winters of 1991–92 and 1994–95 by forcing the model at 100 hPa with observed geopotential height. The authors assess the model’s performance quantitatively by comparing the simulations with the United Kingdom Meteorological Office (UKMO) assimilated stratosphere– troposphere data. Time-mean, zonal-mean temperatures are generally within 5 K and winds within 5 m s⁻¹; transient features, such as wave growth, are mostly simulated well. The phase accuracy of planetary-scale waves declines with altitude and wavenumber, and the model has difficulty correctly simulating traveling anticyclones in the upper stratosphere. The authors examine the minor warming of January 1995 which was unusual in its depth and development and which the model simulated fairly well. The authors also examine the minor warming of January 1992, which the model missed, and a major warming in February 1992 that occurred in the model but not in the observations. Close