Global-scale remote sensing of water isotopologues in the troposphere: representation of first-order isotope effects

Abstract

Abstract. Over the last decade, global-scale data sets of atmospheric water vapor isotopologues (HDO) have become available from different remote sensing instruments. Due to the observational geometry and the spectral ranges that are used, few satellites sample water isotopologues in the lower troposphere, where the bulk of hydrological processes within the atmosphere take place. Here, we compare three satellite HDO data sets, two from the Tropospheric Emission Spectrometer (TES retrieval version 4 and 5) and one from SCIAMACHY (SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY), with results from the atmospheric global circulation model ECHAM4 (European Centre HAMburg 4). We examine a list of known isotopologue effects to qualitatively benchmark the various observational data sets. TES version 5 (TES V5 ), TES version 4 (TES V4 ), SCIAMACHY, ECHAM, and ECHAM convolved with averaging kernels of TES version 5 (ECHAM AK5 ) successfully reproduced a number of established isotopologue effects such as the latitude effect, the amount effect, and the continental effect. The improvement of TES V5 over TES V4 is confirmed by the steeper latitudinal gradient at higher latitudes in agreement with SCIAMACHY. Also the representation of other features of the water isotopologue cycle, such as the seasonally varying signal in the tropics due to the movement of the Intertropical Convergence Zone (ITCZ), is improved in TES V5 and SCIAMACHY compared to TES V4 . A known humidity bias due to the cross correlation of H 2 O and HDO measurements, which is of particular importance for instruments with low sensitivity close to the surface, was analyzed by applying either a humidity bias correction or a suitable a posteriori analysis. We suggest that the qualitative and quantitative tests carried out in this study could become benchmark tests for evaluation of future satellite isotopologue data sets.

Stable isotopes in atmospheric water vapor and applications to the hydrologic cycle

“…R air is the in situ/modeled profile mapped to the retrieval altitude (or pressure) grid and R a the a priori profile. More details on this error calculations and convolution operations can be found in a variety of TES papers [e.g., Worden et al , ; Risi et al , ; Sutanto et al , ].…”

Accomplishments of the MUSICA project to provide accurate, long-term, global and high-resolution observations of tropospheric {H<sub>2</sub>O,<i>δ</i>D} pairs – a review

“…Berkelhammer et al, 2012;Tuinenburg et al, 2015) or for drawing conclusions on vertical mixing processes (e.g. Noone, 2012;Risi et al, 2012a;Sutanto et al, 2015). However, there are very few studies so far where attempts have been made to empirically validate these {H 2 O,δD} pairs Lacour et al, 2015).…”

“…Worden et al, 2007), for investigating the dynamics of the MaddenJulian oscillation (e.g. Berkelhammer et al, 2012;Tuinenburg et al, 2015) or for drawing conclusions on vertical mixing processes (e.g. Noone, 2012;Risi et al, 2012a;Sutanto et al, 2015).…”

Impact of deep convection on the isotopic amount effect in tropical precipitation

“…The midtropospheric depletion of the δD vapor in the Tau08 simulation is due to the increased net condensation through shallow and stratiform schemes. Furthermore, the suppressed deep convection may reduce the uplifting of enriched vapor from the lower troposphere to middle troposphere [ Sutanto et al ., ], leading to more negative δD vapor values in the midtroposphere compared to the control simulation.…”

“…Several studies using observational data [e.g., Kurita , ] and climate models equipped with tracers for water isotope ratios [ Vuille et al ., , ; Bony et al ., ; Risi et al ., , , , ; Lee and Fung , ; Tindall et al ., ] have attempted to quantify the present‐day amount effect and to study the physical mechanism behind the amount effect. These studies explain amount effect based on (i) the increased condensation and rainout with heavy precipitation [ Vuille et al ., ]; (ii) reevaporation of precipitation and enhanced recycling of this isotopically depleted vapor in unsaturated downdrafts during intense convection [ Risi et al ., ]; (iii) drop‐size‐dependent partial equilibration of raindrops below the cloud base [ Lee and Fung , ]; (iv) the dependence of isotope ratios of precipitation on the converged vapor, with the increased moisture convergence during the convective events, than on the vapor from the local evaporation [ Lee et al ., ; Moore et al ., ]; and (v) increased rain amount and reduced proportion of reevaporation of falling raindrops in the convective systems [ Sutanto et al ., ]. Event‐based observations from tropical stations over land [ Lekshmy et al ., ] and ocean [ Kurita , ] find the dominant effect of the presence of organized convective systems on the amount effect.…”