Isotopic measurements in water vapor, precipitation, and seawater during EUREC⁴A

Abstract

Abstract. In early 2020, an international team set out to investigate trade wind cumulus and their coupling to the large-scale circulation through the field campaign EUREC4A: ElUcidating the RolE of Clouds‐Circulation Coupling in ClimAte. Focused on the western tropical Atlantic near Barbados, EUREC4A deployed a number of innovative observational strategies, including a large network of water isotopic measurements, to study the tropical shallow convective environment. The goal of the isotopic measurements was to elucidate processes that regulate the hydroclimate state – for example, by identifying moisture sources, quantifying mixing between atmospheric layers, characterizing the microphysics that influence the formation and persistence of clouds and precipitation, and providing an extra constraint in the evaluation of numerical simulations. During EUREC4A, researchers deployed seven water vapor isotopic analyzers on two aircraft, on three ships, and at the Barbados Cloud Observatory (BCO). Precipitation was also collected for isotopic analysis at BCO and from aboard four ships. In addition, three ships collected seawater for isotopic analysis. All told, the in situ data span the period 5 January through 22 February 2020 and cover the approximate area 6 to 16° N and −50 to −60° W. Moreover, water vapor isotope ratios were measured from a few meters to nearly 8 km above sea level. This paper describes the full EUREC4A isotopic in situ data collection – providing extensive information about sampling strategies and data uncertainties – and also guides readers to complementary remotely sensed water vapor isotope ratios. DOIs for the multiple isotopic datasets are provided in Sect. 5 Data Availability.

Tracking Shallow Convective Mixing and Its Influence on Low‐Level Clouds With Stable Water Isotopes in Vapor

“…As an additional check on how well the δD vertical gradient represents shallow convective mixing, gradients were calculated from the water isotopic data collected by the NOAA P‐3 aircraft during the 2020 EUREC 4 A field campaign. One of the primary science goals of EUREC 4 A was to evaluate shallow convective mixing in the western tropical Atlantic, near the island of Barbados (Bailey et al., 2022; Stevens et al., 2021). Figure 7 shows mean profiles (with 10‐hPa vertical spacing) of relative humidity, equivalent potential temperature, and δD for the 11 P‐3 flights (Pincus et al., 2021).…”

EUREC<sup>4</sup>A observations from the SAFIRE ATR42 aircraft

“…The quality control, the calibration and the processing of the datasets derived from the core instrumentation of the ATR (referred to as SAFIRE-CORE, SAFIRE-RADIATION, SAFIRE-CLIMAT and SAFIRE-CAMERA), from the microphysical probes (UHSAS, ultra-high-sensitivity aerosol spectrometer, and PMA, Microphysics Airborne Platform), from the Doppler cloud radars (BASTA, Bistatic Radar System for Atmospheric Studies, and RASTA, RAdar Sys-Tem Airborne) and from the combined radar-lidar dataset (BASTALIAS) are presented below. The processing of the lidar dataset (ALiAS, Airborne Lidar for Atmospheric Studies), the turbulence dataset (SAFIRE-TURB) and the isotopic dataset (Picarro) is fully described in separate papers (respec-tively Chazette et al, 2020;Brilouet et al, 2021;Bailey et al, 2022); only the main aspects of these datasets are summarized below.…”

“…In addition to characterizing the meteorological, turbulent, microphysical, cloud and radiative properties of the atmosphere, the ATR measured the water-isotopic composition of the atmosphere using a customized fast-response cavity ringdown spectrometer from Picarro (version L2130-i). This effort took place as part of a wider EUREC 4 A-iso initiative involving multiple platforms and instruments (Stevens et al, 2021;Bailey et al, 2022). The rationale for isotopic measurements is that by quantifying the relative content of isotopically heavy ( 1 H 2 H 16 O, 1 H 18 2 O) and light ( 1 H 16 2 O) water molecules in the atmosphere, it is possible to get information about the transport, mixing and phase changes of water.…”

“…A time lag of between 6 and 15 s was found for the Picarro with synchronized computer clocks and was corrected in the post-processing. More details on the setup can be found in Bailey et al (2022).…”

The Virga-Sniffer – a new tool to identify precipitation evaporation using ground-based remote-sensing observations

“…done byXie et al (2016);Tridon et al (2017).Other possible applications of the Virga-Sniffer include enhancing studies of precipitation evaporation in the context of cold pools and cloud organization within the frame of EUREC 4 A as e.g. done byVogel et al (2021);Touzé-Peiffer et al (2022).Additionally, studying precipitation and virga characteristics coupled with water vapour isotopic measurements which was also a focus of EUREC 4 A(Bailey et al, 2022) can help to discern the balance of moist processes which set the humidity profiles.While the Virga-Sniffer was developed within the context of EUREC 4 A and the shown results here focus on warm clouds, the tool is highly modular and configurable and thus applicable to study precipitation evaporation or sublimation originating from other cloud types such as ice and mixed-phase-clouds and can be used in other geographic settings such as orographic terrain or the Arctic. As a near-future goal, we would like to apply it to the long-term BCO remote-sensing dataset to contrast precipitation evaporation in the dry and wet season.…”