In situ sounding of radiative flux profiles through the Arctic lower troposphere

Abstract

In situ profiles and fixed-altitude time series of all four components of net radiation were obtained at Ny-Ålesund, Svalbard (78.9° N, 11.9° E), in the period May 04–21, 2015. Measurements were performed using adapted high-quality instrumentation classified as “secondary standard” carried by a tethered balloon system. Balloon-lifted measurements of albedo under clear-sky conditions demonstrate the local dependence on altitude and on the surface inhomogeneity of this parameter over coastal terrain of Ny-Ålesund. Depending on the surface composition within the sensor’s footprint near the coastline, the albedo over predominantly snow-covered surfaces was found to decrease to 0.548 and 0.452 at 494 m and 881 m altitude compared with 0.731 and 0.788 measured with near-surface references, respectively. Albedo profiles show an all-sky maximum at 150 m above surface level due to local surface inhomogeneity, and an averaged vertical change rate of − 0.040/100 up to 750 m aboveground level (clear sky) and − 0.034/100 m (overcast). Profiling of arctic low-level clouds reveals distinct vertical gradients in all radiative fluxes but longwave upward at the cloud top. Observed radiative cooling at the top of a partly dissolving stratus cloud with heating rates of − 40.4 to − 62.1 Kd−1 in subsequent observations is exemplified.

Tethered balloon-borne observations of thermal-infrared irradiance and cooling rate profiles in the Arctic atmospheric boundary layer

“…5c) shows weak oscillations typically below ± 1 K d −1 centered on the zero line. This case corresponds to the radiative equilibrium where surface and cloud base emit a similar amount of radiation, as previously shown for similar cloud conditions on sea ice (Egerer et al, 2019) and in Ny-Ålesund (Becker et al, 2020). The average profile obtained through low-level water-bearing clouds in summer shows the radiative cooling rates below, in, and above a vertically normalized cloud (Fig.…”

“…While most of the literature discusses the cloud radiative effect at the surface, its height dependence in the atmospheric boundary layer (ABL) is mostly not considered, although it may be significant because of local radiative energy sources and sinks at different altitudes (Curry, 1986;Yamamoto et al, 1995;Asano et al, 2004;Philipona et al, 2020). For example, Turner et al (2018) showed that the vertical structure of irradiance and radiative cooling rate profiles depends on the atmospheric state.…”

“…However, these observations become particularly challenging in the harsh Arctic environmental conditions. Nevertheless, in recent years a significant number of data were collected with the help of aircraft (Ehrlich et al, 2019;Wendisch et al, , 2023bBecker et al, 2023), free-flying balloons (Philipona et al, 2020), and tethered balloons (Lawson et al, 2011;Sikand et al, 2013;Dexheimer et al, 2019;Becker et al, 2020;Inoue et al, 2021). In particular, combined measurements of thermodynamic properties (Egerer et al, 2021), broadband irradiances (Lonardi et al, 2022), turbulence (Egerer et al, 2019(Egerer et al, , 2023, and aerosol particle properties (Pilz et al, 2022) were obtained with the tethered balloon-borne system BELUGA (Balloon-bornE moduLar Utility for profilinG the lower Atmosphere; Egerer et al, 2019).…”

Determining the surface mixing layer height of the Arctic atmospheric boundary layer during polar night in cloudless and cloudy conditions

“…1b. The balloon has a volume of about 9 m 3 and allows to lift a modular scientific payload of up to 4 kg (Becker et al, 2020). The setup enables continuously vertical profiling of the lowermost 1.5 km of the atmosphere with a climbing rate of 1 to 2 m s −1 .…”

Evaluation of methods to determine the surface mixing layer height of the atmospheric boundary layer in the central Arctic during polar night and transition to polar day in cloudless and cloudy conditions

“…An overview of the atmospheric measurements is given by Shupe et al (2022), and information about the sea ice and oceanographic aspects is summarized by Nicolaus et al (2022) and Rabe et al (2022). Figure 1a shows the course of the drift of RV Polarstern in winter and spring when the tethered balloon Miss Piggy (Becker et al, 2020) was deployed from the ice floe close to RV Polarstern.…”