The isotopic signature of monsoon conditions, cloud modes, and rainfall type

Zwart, Costijn, Munksgaard, Niels C., Protat, Alain, Kurita, Naoyuki, Lambrinidis, Dionisia, and Bird, Michael I. (2018) The isotopic signature of monsoon conditions, cloud modes, and rainfall type. Hydrological Processes, 32 (15). pp. 2296-2303.

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Abstract

This work provides a comprehensive physically based framework for the interpretation of the north Australian rainfall stable isotope record (δ18O and δ2H). Until now, interpretations mainly relied on statistical relationships between rainfall amount and isotopic values on monthly timescales. Here, we use multiseason daily rainfall stable isotope and high resolution (10 min) ground‐based C‐band polarimetric radar data and show that the five weather types (monsoon regimes) that constitute the Australian wet season each have a characteristic isotope ratio. The data suggest that this is not only due to changes in regional rainfall amount during these regimes but, more importantly, is due to different rain and cloud types that are associated with the large scale circulation regimes. Negative (positive) isotope anomalies occurred when stratiform rainfall fractions were large (small) and the horizontal extent of raining areas were largest (smallest). Intense, yet isolated, convective conditions were associated with enriched isotope values whereas more depleted isotope values were observed when convection was widespread but less intense. This means that isotopic proxy records may record the frequency of which these typical wet season regimes occur. Positive anomalies in paleoclimatic records are most likely associated with periods where continental convection dominates and convection is sea‐breeze forced. Negative anomalies may be interpreted as periods when the monsoon trough is active, convection is of the oceanic type, less electric, and stratiform areas are wide spread. This connection between variability of rainfall isotope anomalies and the intrinsic properties of convection and its large‐scale environment has important implications for all fields of research that use rainfall stable isotopes.

Item ID: 54937
Item Type: Article (Research - C1)
ISSN: 1099-1085
Keywords: climate, clouds, convection, hydrology, isotopes, monsoon, palaeoclimatology, rainfall
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Copyright Information: Copyright © 2018 John Wiley & Sons, Ltd.
Additional Information:

This article also appears in Virtual Special Issue "Stable Isotopes in hydrological studies in the Tropics" (see link in Related URLs field).

Funders: Australian Research Council (ARC)
Projects and Grants: ARC FL140100044
Date Deposited: 08 Aug 2018 07:38
FoR Codes: 04 EARTH SCIENCES > 0401 Atmospheric Sciences > 040102 Atmospheric Dynamics @ 50%
04 EARTH SCIENCES > 0401 Atmospheric Sciences > 040105 Climatology (excl Climate Change Processes) @ 50%
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