Evelyn Jäkel
A5073396042- Atmospheric aerosols and clouds
- Atmospheric chemistry and aerosols
- Arctic and Antarctic ice dynamics
- Atmospheric and Environmental Gas Dynamics
- Atmospheric Ozone and Climate
- Cryospheric studies and observations
- Calibration and Measurement Techniques
- Infrared Target Detection Methodologies
- Climate change and permafrost
- Remote Sensing in Agriculture
- Meteorological Phenomena and Simulations
- Aeolian processes and effects
- Spacecraft Design and Technology
- Solar Radiation and Photovoltaics
- Spacecraft and Cryogenic Technologies
- Radiative Heat Transfer Studies
- Polar Research and Ecology
- Impact of Light on Environment and Health
- Climate variability and models
- Methane Hydrates and Related Phenomena
- Ionosphere and magnetosphere dynamics
- Air Quality and Health Impacts
- Spacecraft Dynamics and Control
- Geochemistry and Geologic Mapping
- Urban Heat Island Mitigation
Leipzig University
2015-2024
Max Planck Institute for Meteorology
2013
Johannes Gutenberg University Mainz
2008-2010
Leibniz Institute for Tropospheric Research
2004-2008
National Institute for Public Health and the Environment
2007
German Meteorological Service
2007
Leibniz Association
2006
European Space Research and Technology Centre
1980-1998
Wissenschaftliches Institut der AOK
1990
Abstract Clouds play an important role in Arctic amplification. This term represents the recently observed enhanced warming of relative to global increase near-surface air temperature. However, there are still knowledge gaps regarding interplay between clouds and aerosol particles, surface properties, as well turbulent radiative fluxes that inhibit accurate model simulations climate system. In attempt resolve this so-called cloud puzzle, two comprehensive closely coordinated field studies...
Abstract Between 1 September and 4 October 2014, a combined airborne ground-based measurement campaign was conducted to study tropical deep convective clouds over the Brazilian Amazon rain forest. The new German research aircraft, High Altitude Long Range Research Aircraft (HALO), modified Gulfstream G550, extensive instrumentation were deployed in near Manaus (State of Amazonas). part German–Brazilian Aerosol, Cloud, Precipitation, Radiation Interactions Dynamics Convective Cloud...
Abstract Ice nucleating particles (INPs) affect the radiative properties of cold clouds. Knowledge concerning their concentration above ground level and potential sources is scarce. Here we present first highly temperature resolved ice nucleation spectra airborne samples from an aircraft campaign during late winter in 2018. Most INP featured low levels (<3 · 10 −4 L −1 at −15°C). However, also found concentrations up to 1.8·10 −2 −15°C freezing onsets as high −7.5°C for mainly marine...
Abstract A configuration of the High-Altitude Long-Range Research Aircraft (HALO) as a remote sensing cloud observatory is described, and its use illustrated with results from first second Next-Generation Remote Sensing for Validation (NARVAL) field studies. Measurements NARVAL (NARVAL2) are used to highlight ability HALO, when configured in this fashion, characterize not only distribution water condensate atmosphere, but also impact on radiant energy transfer covarying large-scale...
Abstract. The concept of cloud radiative forcing (CRF) is commonly applied to quantify the impact clouds on surface energy budget (REB). In Arctic, specific interactions between microphysical and macrophysical properties strongly modify warming or cooling effect clouds, complicating estimate CRF obtained from observations models. Clouds tend increase broadband albedo over snow sea ice surfaces compared cloud-free conditions. However, this not adequately considered in derivation Arctic so...
Abstract Melt ponds forming on Arctic sea ice in summer significantly reduce the surface albedo and impact heat mass balance of ice. Therefore, their areal coverage, which can undergo rapid change, is crucial to monitor. We present a revised method extract melt pond fraction (MPF) from Sentinel‐2 satellite imagery, evaluated by MPF products higher‐resolution helicopter‐borne imagery. The analysis evolution during MOSAiC campaign 2020, shows split Central Observatory (CO) into level highly...
Surface reflectance (SR) estimation is the most critical preprocessing step for deriving geophysical parameters in multi-sensor remote sensing. Most state-of-the-art SR methods, such as vector version of Second Simulation Satellite Signal Solar Spectrum (6SV) radiative transfer (RT) model, depend on accurate information aerosol and atmospheric gases. In this study, a Simplified Robust Reflectance Estimation Method (SREM) based equations from 6SV RT without integrating particles gasses,...
Abstract. Vertical profiles of the cloud particle phase state in tropical deep-convective clouds (DCCs) were investigated using airborne solar radiation data collected by German research aircraft HALO during ACRIDICON-CHUVA campaign, which was conducted over Brazilian Amazon September 2014. A discrimination retrieval based on imaging spec-troradiometer measurements side spectral reflectivity applied to DCCs under different aerosol conditions. From results height mixed layer determined. The...
Abstract. The Arctic CLoud Observations Using airborne measurements during polar Day (ACLOUD) campaign was carried out north-west of Svalbard (Norway) between 23 May and 6 June 2017. objective ACLOUD to study boundary layer mid-level clouds their role in amplification. Two research aircraft (Polar 5 6) jointly performed 22 flights over the transition zone open ocean closed sea ice. Both were equipped with identical instrumentation for basic meteorological parameters, as well turbulent...
Abstract. Global warming is amplified in the Arctic. However, numerical models struggle to represent key processes that determine Arctic weather and climate. To collect data help constrain models, HALO–(𝒜𝒞)3 aircraft campaign was conducted over Norwegian Greenland seas, Fram Strait, central Ocean March April 2022. The focused on one specific challenge posed by namely reasonable representation of transformations air masses during their meridional transport into out via northward moist-...
Airborne measurements of the ratio spectral upward and downward irradiances (so‐called albedo) are used to derive areal surface albedo in wavelength range from 330 1670 nm. The data were collected over different sea land surfaces cloudless atmospheric conditions during three field campaigns. Measurements Albedometer (developed at IfT) NASA Solar Spectral Flux Radiometer (SSFR) employed. radiative transfer calculations show that scattering absorption within layer beneath flight level...
Two airborne field campaigns focusing on observations of Arctic mixed-phase clouds and boundary layer processes their role with respect to amplification have been carried out in spring 2019 late summer 2020 over the Fram Strait northwest Svalbard. The latter campaign was closely connected Multidisciplinary drifting Observatory for Study Climate (MOSAiC) expedition. Comprehensive datasets cloudy atmosphere collected by operating remote sensing instruments, in-situ probes, instruments...
Abstract. The global warming is amplified in the Arctic. To collect data that help to constrain weather and climate models, which often do not realistically represent enhanced Arctic warming, HALO-(AC)³ aircraft campaign was conducted March April 2022 over Norwegian Greenland Seas, Fram Strait, central Ocean. Observations were made areas of open ocean, marginal sea ice zone, ice. Two low-flying one long-range, high-altitude research have been employed. Whenever possible, three flown...
Abstract. The combination of downward-looking airborne lidar, radar, microwave, and imaging spectrometer measurements was exploited to characterize the vertical small-scale (down 10 m) horizontal distribution thermodynamic phase low-level Arctic mixed-layer clouds. Two cloud cases observed in a cold air outbreak warm advection event during CLoud Observations Using polar Day (ACLOUD) campaign were investigated. Both exhibited typical mixed-phase structure with mostly liquid water droplets at...
Abstract. Low-level airborne observations of the Arctic surface radiative energy budget are discussed. We focus on terrestrial part budget, quantified by thermal-infrared net irradiance (TNI). The data were collected in cloudy and cloud-free conditions over vicinity marginal sea ice zone (MIZ) close to Svalbard during two aircraft campaigns conducted spring 2019 early summer 2017. measurements, complemented ground-based available from literature transfer simulations, used evaluate influence...
The reflection, absorption, and transmittance of shortwave solar radiation by sea ice play crucial roles in physical biological processes the ice-covered Arctic Ocean atmosphere. These sea-ice optical properties, particularly during melt season, significantly impact energy fluxes within total budget coupled atmosphere-ice-ocean system. We analyzed data from autonomous drifting stations to investigate seasonal evolution spectral albedo, transmittance, absorptivity for different sea-ice, snow,...
Abstract. The sensitivity of passive remote sensing measurements to retrieve microphysical parameters convective clouds, in particular their thermodynamic phase, is investigated by three-dimensional (3-D) radiative transfer simulations. effects different viewing geometries and vertical distributions the cloud properties are investigated. Measurement examples spectral solar radiance reflected sides (passive) near-infrared (NIR) range performed together with collocated lidar observations...
Abstract. For large-scale and long-term Arctic climate simulations appropriate parameterization of the surface albedo is required. Therefore, sea ice (SIS) coupled regional model HIRHAM–NAOSIM was examined against broadband measurements performed during joint ACLOUD (Arctic CLoud Observations Using airborne polar Day) PASCAL (Physical feedbacks boundary layer, Sea ice, Cloud AerosoL) campaigns, which were in May–June 2017 north Svalbard. The SIS tested using measured quantities prognostic...
Abstract. This case study explores the evolution of clouds during an Arctic cold air outbreak in Fram Strait region observed HALO-(𝒜𝒞)3 aircraft campaign. Our research provides information about formation, structure, micro- and macrophysical properties, radiative effects investigates role vertical wind shear buoyancy forces transition from regular cloud streets to rather isotropic patterns. findings show that lower horizontal boundary layer speeds (< 12 m s-1) disrupt formation streets,...
Vegetation indices (VIs) derived from ground-based or unmanned aerial vehicle measurements use relative reflectance obtained by flying over well-defined panels (RP). The RP overflights provide a form of transfer calibration to determine reflectances the actual vegetated areas. It is assumed that environmental conditions, i.e., solar zenith angle (SZA) and cloud optical thickness (COT), remain constant between overflights. During typical 10-minute intervals overflights, COT varies especially...
Abstract. The HALO–(𝒜𝒞)3 aircraft campaign was carried out in March and April 2022 over the Norwegian Greenland seas, Fram Strait, central Arctic Ocean. Three research – High Altitude Long Range Research Aircraft (HALO), Polar 5, 6 performed 54 partly coordinated flights on 23 flight days areas of open ocean, marginal sea ice zone (MIZ), ice. general objective to quantify evolution air mass properties during moist warm-air intrusions (WAIs) cold-air outbreaks (CAOs). To obtain a...
Abstract. In September 2002, the first INSPECTRO campaign to study influence of clouds on spectral actinic flux in lower troposphere was carried out East Anglia, England. Measurements flux, irradiance and aerosol cloud properties were made from four ground stations by aircraft. The radiation measurements modelled using uvspec model ancillary data. For cloudless conditions, reproduced 1-D radiative transfer modelling within measurement uncertainties about ±10%. overcast days, ground-based...
Abstract. Arctic summer sea ice experiences rapid changes in its sea-ice concentration, surface albedo, and the melt pond fraction. This affects energy balance of region demands an accurate knowledge those characteristics climate models. In this paper, broadband albedo (300–3000 nm) is derived from MEdium Resolution Imaging Spectrometer (MERIS) optical swath data by transforming spectral as output Melt Pond Detector (MPD) algorithm with a newly developed spectral-to-broadband conversion...
Abstract. The surface reflection of solar radiation comprises an important boundary condition for radiative transfer simulations. In polar regions above snow surfaces, the is particularly anisotropic due to low Sun elevations and highly scattering phase function crystals. characterization this anisotropy essential satellite remote sensing over both Arctic Antarctica. To quantify angular properties, hemispherical-directional reflectance factor (HDRF) surfaces was derived from airborne...