scholarly journals Sources of seasonal variability in tropical upper troposphere and lower stratosphere water vapor and ozone: Inferences from the Ticosonde data set at Costa Rica

2015 ◽  
Vol 120 (18) ◽  
pp. 9684-9701 ◽  
Author(s):  
Mark R. Schoeberl ◽  
Henry B. Selkirk ◽  
Holger Vömel ◽  
Anne R. Douglass
Keyword(s):  
Water Vapor ◽  
Costa Rica ◽  
Seasonal Variability ◽  
Lower Stratosphere ◽  
Data Set ◽  
Upper Troposphere ◽  
Tropical Upper Troposphere

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 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 (3) ◽  
pp. 10353-10396 ◽  
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. A sensitivity analysis reveals that the DIAL profiles have 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 show 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 16 km, 1 to 2 km beneath the local tropopause. A high-resolution (2 km horizontal, ~200 m 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

2018 ◽  
Author(s):  
Edward W. Tian ◽  
Hui Su ◽  
Baijun Tian ◽  
Jonathan H. Jiang
Keyword(s):  
Water Vapor ◽  
Lower Stratosphere ◽  
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 hPa 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 Nino Southern Oscillation (ENSO) and quasi-biennial oscillation (QBO). Our analysis shows that ENSO’s impact on the interannual tropical water vapor anomalies is strong in the upper troposphere (~215 to ~120 hPa) and near the tropopause (~110 to ~90 hPa) with a ~3-month lag but weak in the lower and middle stratosphere (~80 to ~6 hPa). In contrast, QBO has a large impact on the interannual tropical water vapor anomalies in the lower and middle stratosphere with an upward propagating signal starting at the tropopause (100 hPa), peaking first in the lower stratosphere near 68 hPa with a ~7-month lag and then in the middle stratosphere near 15 hPa with a ~24-month lag. The phase lag is based on the 30-hPa QBO index and should be different from that found by previous studies based on the 50-hPa QBO index. In the upper troposphere, interannual tropical water vapor anomalies are positive during the warm ENSO phases but negative during the cold ENSO phases no matter what QBO phases are. Near the tropopause, interannual tropical water vapor anomalies are different depending on different ENSO and QBO phase combinations. In the lower and middle stratosphere, interannual tropical water vapor anomalies are mainly determined by QBO instead of ENSO. For the easterly QBO phases, interannual tropical water vapor anomalies are positive in the lower stratosphere but negative in the middle stratosphere. Vice versa for the westerly QBO phases.

scholarly journals Effect of tropical cyclones on the Stratosphere-Troposphere Exchange observed using satellite observations over north Indian Ocean

2016 ◽  
Author(s):  
M. Venkat Ratnam ◽  
S. Ravindra Babu ◽  
S. S. Das ◽  
Ghouse Basha ◽  
B. V. Krishnamurthy ◽  
...  
Keyword(s):  
Water Vapor ◽  
Indian Ocean ◽  
Tropical Cyclones ◽  
Lower Stratosphere ◽  
North Indian Ocean ◽  
Satellite Observations ◽  
Upper Troposphere ◽  
North West ◽  
The North ◽  
The Impact

Abstract. Tropical cyclones play an important role in modifying the tropopause structure and dynamics as well as stratosphere-troposphere exchange (STE) process in the Upper Troposphere and Lower Stratosphere (UTLS) region. In the present study, the impact of cyclones that occurred over the North Indian Ocean during 2007–2013 on the STE process is quantified using satellite observations. Tropopause characteristics during cyclones are obtained from the Global Positioning System (GPS) Radio Occultation (RO) measurements and ozone and water vapor concentrations in UTLS region are obtained from Aura-Microwave Limb Sounder (MLS) satellite observations. The effect of cyclones on the tropopause parameters is observed to be more prominent within 500 km from the centre of cyclone. In our earlier study we have observed decrease (increase) in the tropopause altitude (temperature) up to 0.6 km (3 K) and the convective outflow level increased up to 2 km. This change leads to a total increase in the tropical tropopause layer (TTL) thickness of 3 km within the 500 km from the centre of cyclone. Interestingly, an enhancement in the ozone mixing ratio in the upper troposphere is clearly noticed within 500 km from cyclone centre whereas the enhancement in the water vapor in the lower stratosphere is more significant on south-east side extending from 500–1000 km away from the cyclone centre. We estimated the cross-tropopause mass flux for different intensities of cyclones and found that the mean flux from stratosphere to troposphere for cyclonic stroms is 0.05 ± 0.29 × 10−3 kg m−2 and for very severe cyclonic stroms it is 0.5 ± 1.07 × 10−3 kg m−2. More downward flux is noticed in the north-west and south-west side of the cyclone centre. These results indicate that the cyclones have significant impact in effecting the tropopause structure, ozone and water vapour budget and consequentially the STE in the UTLS region.

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