scholarly journals Intraseasonal variations of water vapor in the tropical upper troposphere and tropopause region

2000 ◽  
Vol 105 (D13) ◽  
pp. 17457-17470 ◽  
Author(s):  
Philip W. Mote ◽  
Hannah L. Clark ◽  
Timothy J. Dunkerton ◽  
Robert S. Harwood ◽  
Hugh C. Pumphrey
Keyword(s):  
Water Vapor ◽  
Upper Troposphere ◽  
Intraseasonal Variations ◽  
Tropopause Region ◽  
Tropical Upper Troposphere

scholarly journals A statistical analysis of the influence of deep convection on water vapor variability in the tropical upper troposphere

2009 ◽  
Vol 9 (15) ◽  
pp. 5847-5864 ◽  
Author(s):  
J. S. Wright ◽  
R. Fu ◽  
A. J. Heymsfield
Keyword(s):  
Water Vapor ◽  
Deep Convection ◽  
Tropical Rainfall Measuring Mission ◽  
Upper Troposphere ◽  
Ambient Relative Humidity ◽  
Wide Range ◽  
Ice Water Content ◽  
The Tropics ◽  
Ice Water ◽  
Tropical Upper Troposphere

Abstract. The factors that control the influence of deep convective detrainment on water vapor in the tropical upper troposphere are examined using observations from multiple satellites in conjunction with a trajectory model. Deep convection is confirmed to act primarily as a moisture source to the upper troposphere, modulated by the ambient relative humidity (RH). Convective detrainment provides strong moistening at low RH and offsets drying due to subsidence across a wide range of RH. Strong day-to-day moistening and drying takes place most frequently in relatively dry transition zones, where between 0.01% and 0.1% of Tropical Rainfall Measuring Mission Precipitation Radar observations indicate active convection. Many of these strong moistening events in the tropics can be directly attributed to detrainment from recent tropical convection, while others in the subtropics appear to be related to stratosphere-troposphere exchange. The temporal and spatial limits of the convective source are estimated to be about 36–48 h and 600–1500 km, respectively, consistent with the lifetimes of detrainment cirrus clouds. Larger amounts of detrained ice are associated with enhanced upper tropospheric moistening in both absolute and relative terms. In particular, an increase in ice water content of approximately 400% corresponds to a 10–90% increase in the likelihood of moistening and a 30–50% increase in the magnitude of moistening.

Multimodel Analysis of the Water Vapor Feedback in the Tropical Upper Troposphere

2006 ◽  
Vol 19 (20) ◽  
pp. 5455-5464 ◽  
Author(s):  
Ken Minschwaner ◽  
Andrew E. Dessler ◽  
Parnchai Sawaengphokhai
Keyword(s):  
Water Vapor ◽  
Relative Humidity ◽  
Climate Models ◽  
Global Climate ◽  
Global Climate Models ◽  
Sea Surface ◽  
Specific Humidity ◽  
Upper Troposphere ◽  
The Mean ◽  
Tropical Upper Troposphere

Abstract Relationships between the mean humidity in the tropical upper troposphere and tropical sea surface temperatures in 17 coupled ocean–atmosphere global climate models were investigated. This analysis builds on a prior study of humidity and surface temperature measurements that suggested an overall positive climate feedback by water vapor in the tropical upper troposphere whereby the mean specific humidity increases with warmer sea surface temperature (SST). The model results for present-day simulations show a large range in mean humidity, mean air temperature, and mean SST, but they consistently show increases in upper-tropospheric specific humidity with warmer SST. The model average increase in water vapor at 250 mb with convective mean SST is 44 ppmv K−1, with a standard deviation of 14 ppmv K−1. Furthermore, the implied feedback in the models is not as strong as would be the case if relative humidity remained constant in the upper troposphere. The model mean decrease in relative humidity is −2.3% ± 1.0% K−1 at 250 mb, whereas observations indicate decreases of −4.8% ± 1.7% K−1 near 215 mb. These two values agree within the respective ranges of uncertainty, indicating that current global climate models are simulating the observed behavior of water vapor in the tropical upper troposphere with reasonable accuracy.

scholarly journals First airborne water vapor lidar measurements in the tropical upper troposphere and mid-latitudes lower stratosphere: accuracy evaluation and intercomparisons with other instruments

2008 ◽  
Vol 8 (17) ◽  
pp. 5245-5261 ◽  
Author(s):  
C. Kiemle ◽  
M. Wirth ◽  
A. Fix ◽  
G. Ehret ◽  
U. Schumann ◽  
...  
Keyword(s):  
Water Vapor ◽  
Lower Stratosphere ◽  
Average Distance ◽  
Tropical Convection ◽  
Water Vapor Transport ◽  
Mixing Ratio ◽  
Upper Troposphere ◽  
Research Aircraft ◽  
Tropical Upper Troposphere

Abstract. In the tropics, deep convection is the major source of uncertainty in water vapor transport to the upper troposphere and into the stratosphere. Although accurate measurements in this region would be of first order importance to better understand the processes that govern stratospheric water vapor concentrations and trends in the context of a changing climate, they are sparse because of instrumental shortcomings and observational challenges. Therefore, the Falcon research aircraft of the Deutsches Zentrum für Luft- und Raumfahrt (DLR) flew a zenith-viewing water vapor differential absorption lidar (DIAL) during the Tropical Convection, Cirrus and Nitrogen Oxides Experiment (TROCCINOX) in 2004 and 2005 in Brazil. The measurements were performed alternatively on three water vapor absorption lines of different strength around 940 nm. These are the first aircraft DIAL measurements in the tropical upper troposphere and in the mid-latitudes lower stratosphere. Sensitivity analyses reveal an accuracy of 5% between altitudes of 8 and 16 km. This is confirmed by intercomparisons with the Fast In-situ Stratospheric Hygrometer (FISH) and the Fluorescent Advanced Stratospheric Hygrometer (FLASH) onboard the Russian M-55 Geophysica research aircraft during five coordinated flights. The average relative differences between FISH and DIAL amount to −3%±8% and between FLASH and DIAL to −8%±14%, negative meaning DIAL is more humid. The average distance between the probed air masses was 129 km. The DIAL is found to have no altitude- or latitude-dependent bias. A comparison with the balloon ascent of a laser absorption spectrometer gives an average difference of 0%±19% at a distance of 75 km. Six tropical DIAL under-flights of the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) on board ENVISAT reveal a mean difference of −8%±49% at an average distance of 315 km. While the comparison with MIPAS is somewhat less significant due to poorer comparison conditions, the agreement with the in-situ hygrometers provides evidence of the excellent quality of FISH, FLASH and DIAL. Most DIAL profiles exhibit a smooth exponential decrease of water vapor mixing ratio in the tropical upper troposphere to lower stratosphere transition. The hygropause with a minimum mixing ratio of 2.5 µmol/mol is found between 15 and 17 km. A high-resolution (2 km horizontal, 0.2 km vertical) DIAL cross section through the anvil outflow of tropical convection shows that the ambient humidity is increased by a factor of three across 100 km.

scholarly journals Interannual variations of water vapor in the tropical upper troposphere and the lower and middle stratosphere and their connections to ENSO and QBO

2019 ◽  
Vol 19 (15) ◽  
pp. 9913-9926 ◽  
Author(s):  
Edward W. Tian ◽  
Hui Su ◽  
Baijun Tian ◽  
Jonathan H. Jiang
Keyword(s):  
Water Vapor ◽  
Southern Oscillation ◽  
Phase Lag ◽  
Interannual Variations ◽  
Quasi Biennial Oscillation ◽  
Upper Troposphere ◽  
Tropical Water ◽  
Enso Phases ◽  
Middle Stratosphere ◽  
Tropical Upper Troposphere

Abstract. In this study, we analyze the Aura Microwave Limb Sounder water vapor data in the tropical upper troposphere and the lower and middle stratosphere (UTLMS) (from 215 to 6 hPa) for the period from August 2004 to September 2017 using time-lag regression analysis and composite analysis to explore the interannual variations of tropical UTLMS water vapor and their connections to El Niño–Southern Oscillation (ENSO) and quasi-biennial oscillation (QBO). Our analysis shows that the interannual tropical UTLMS water vapor anomalies are strongly related to ENSO and QBO which together can explain more than half (∼ 50 %–60 %) but not all variance of the interannual tropical water vapor anomalies. We find that ENSO's impact is strong in the upper troposphere (∼ 215–∼ 120 hPa) and near the tropopause (∼ 110–∼ 90 hPa), with a ∼ 3-month lag but weak in the lower and middle stratosphere (∼ 80 to ∼ 6 hPa). In contrast, QBO's role is large in the lower and middle stratosphere, with an upward-propagating signal starting at the tropopause (100 hPa) with a ∼ 2-month lag, peaking in the middle stratosphere near 15 hPa with a ∼ 21-month lag. The phase lag is based on the 50 hPa QBO index used by many previous studies. This observational evidence supports that the QBO's impact on the tropical stratospheric water vapor is from its modulation on the tropical tropopause temperature and then transported upward with the tape recorder as suggested by many previous studies. In the upper troposphere, ENSO is more important than QBO for the interannual tropical water vapor anomalies that are positive during the warm ENSO phases but negative during the cold ENSO phases. Near the tropopause, both ENSO and QBO are important for the interannual tropical water vapor anomalies. Warm ENSO phase and westerly QBO phase tend to cause positive water vapor anomalies, while cold ENSO phase and easterly QBO phase tend to cause negative water vapor anomalies. As a result, the interannual tropical water vapor anomalies near the tropopause are different depending on different ENSO and QBO phase combinations. In the lower and middle stratosphere, QBO is more important than ENSO for the interannual tropical water vapor anomalies. For the westerly QBO phases, interannual tropical water vapor anomalies are positive near the tropopause and in the lower stratosphere but negative in the middle stratosphere and positive again above. Vice versa for the easterly QBO phases.

scholarly journals A statistical analysis of the influence of deep convection on water vapor variability in the tropical upper troposphere

2009 ◽  
Vol 9 (1) ◽  
pp. 4035-4079
Author(s):  
J. S. Wright ◽  
R. Fu ◽  
A. J. Heymsfield
Keyword(s):  
Water Vapor ◽  
Deep Convection ◽  
Particle Sizes ◽  
Upper Troposphere ◽  
Transition Zones ◽  
Ambient Relative Humidity ◽  
Wide Range ◽  
Temporal And Spatial ◽  
Very High ◽  
Tropical Upper Troposphere

Abstract. The factors that control the influence of deep convective detrainment on water vapor in the tropical upper troposphere are examined using observations from multiple satellites in conjunction with a trajectory model. Deep convection is confirmed to act primarily as a moisture source to the upper troposphere, modulated by the ambient relative humidity (RH). Convective detrainment provides strong moistening at low RH and offsets drying due to subsidence across a wide range of RH. Strong day-to-day moistening and drying takes place most frequently in relatively dry transition zones where the frequency of deep convective events is neither very high nor very low. Many of these strong moistening events can be directly attributed to detrainment from recent tropical convection. The temporal and spatial limits of the convective source are estimated to be about 36–48 h and 600–1500 km, respectively, consistent with the lifetimes of detrainment cirrus clouds. Larger amounts of detrained ice and smaller ice particle sizes are both associated with enhanced upper tropospheric moistening.

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