A systematic assessment of water vapor products in the Arctic: from instantaneous measurements to monthly means

Abstract

Abstract. Water vapor is an important component in the water and energy cycle of the Arctic. Especially in light of Arctic amplification, changes in water vapor are of high interest but are difficult to observe due to the data sparsity of the region. The ACLOUD/PASCAL campaigns performed in May/June 2017 in the Arctic North Atlantic sector offers the opportunity to investigate the quality of various satellite and reanalysis products. Compared to reference measurements at R/V Polarstern frozen into the ice (around 82∘ N, 10∘ E) and at Ny-Ålesund, the integrated water vapor (IWV) from Infrared Atmospheric Sounding Interferometer (IASI) L2PPFv6 shows the best performance among all satellite products. Using all radiosonde stations within the region indicates some differences that might relate to different radiosonde types used. Atmospheric river events can cause rapid IWV changes by more than a factor of 2 in the Arctic. Despite the relatively dense sampling by polar-orbiting satellites, daily means can deviate by up to 50 % due to strong spatio-temporal IWV variability. For monthly mean values, this weather-induced variability cancels out, but systematic differences dominate, which particularly appear over different surface types, e.g., ocean and sea ice. In the data-sparse central Arctic north of 84∘ N, strong differences of 30 % in IWV monthly means between satellite products occur in the month of June, which likely result from the difficulties in considering the complex and changing surface characteristics of the melting ice within the retrieval algorithms. There is hope that the detailed surface characterization performed as part of the recently finished Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) will foster the improvement of future retrieval algorithms.

Case study of a moisture intrusion over the Arctic with the ICOsahedral Non-hydrostatic (ICON) model: resolution dependence of its representation

“…5, larger variabilities in IWV values are found during the AR passage (6 June 2017) compared to the pre-and post-event periods. The differences found in GNSS and HATPRO have also been shown by Crewell et al (2021), with the latter being closer to radiosonde measurements within a long-term assessment. These differences, between the statistics from the observations and the reanalysis and model datasets, are also reflected in the RMSE and MAE values being higher during the AR passage over Ny-Ålesund, indicating the difficulty for the reanalysis and model simulations to represent the accurate amount of humidity in the atmospheric column during the AR passage at Ny-Ålesund.…”

“…Some of this relatively good agreement of ERA5 IWV time series with the radiosonde values might come from the assimilation of observations. However, Crewell et al (2021) showed that Russian radiosonde stations may often be too dry compared to satellite data (e.g. IASI, MIRS).…”

“…Moreover, IWV was derived based on the zenith path delay of Global Navigation Satellite System (GNSS) ground station data (Dick et al, 2001;Gendt et al, 2004) with a temporal resolution of 15 min and an accuracy of 1-2 kg m −2 . Ground-based remote sensing with a HATPRO microwave radiometer enables the retrieval of IWV over Ny-Ålesund every 2 s (Nomokonova et al, 2019a), with an uncertainty of about 0.5 kg m −2 (Crewell et al, 2021) as shown in comparisons to radiosonde measurements. Note that HATPRO provides the water vapour column directly above the station, while GNSS measurements are taken between ground and several GNSS satellites, leading to a footprint of about 30 km (Steinke et al, 2015).…”

Overview of the MOSAiC expedition: Atmosphere

“…A systematic assessment of derived fluxes will be performed as a function of viewing zenith angle, and a series of observation-constrained sensitivity studies will be used to evaluate many of the retrieval assumptions concerning the surface, atmosphere, and cloud properties. Similar evaluations can harness atmospheric observations to evaluate cloud, aerosol, water vapor, and temperature observations from a variety of other satellites (e.g., Crewell et al, 2021). Ultimately, these evaluations will help to improve satellite-based observations and reduce the overall uncertainty of pan-Arctic radiative budgets.…”

Characteristics of Arctic Summer Inversion and Its Correlation with Extreme Sea Ice Anomalies

“…Since the launch of the hyperspectral Atmospheric Infrared Sounder (AIRS) on board the Aqua satellite in 2002, the observational capability to quantify the vertical structure of air temperature from space has been highly improved [23]. A growing number of studies are focused on the assessments (e.g., [24][25][26][27]) and applications of the AIRS vertical air profiles (e.g., [23,[28][29][30][31][32][33][34]) in the polar regions. Among these studies, Arctic temperature inversions are of great attention.…”