Weather
Xavier Calbet (AEMET) presents his work on water vapour variability in the atmosphere and the effect of the variability on the water vapour fields in its vicinity.
Water vapor at small scales (< 6 km) behaves, on average, in an stochastic way. This behavior can be described by simple stochastic models (Gaussian Random Fields). Knowing the variability (or turbulence) of water vapor in a location, mainly via measurements, we can infer the statistical characteristics of water vapor fields in its vicinity. This model will help us in: determining whether water vapor measurements from satellites can be more or less biased, integrate different water vapor measurements coming from differing spatial scales together in a coherent way, estimate the turbulence that is potentially present in the atmosphere. Direct consequences of this concept regarding Nowcasting still need to be explored in the future.
Jan El-Kassar and Cintia Carbajal Henkel (Free University of Berlin) talk about their efforts to develop an optimal estimation algorithm for the 0.865 and 0.914 micrometer bands to retrieve a total column water product.
MTG-FCI will feature a band configuration in the rho-sigma-tau absorption band of water vapour (0.865 and 0.914 microns). We are developing an optimal estimation algorithm for these two bands to retrieve a total column water vapour product, which will be highly sensitive to boundary layer moisture.
We show preliminary results from a first prototype based on COWa (Copernicus Sentinel-3 OLCI Water Vapour) applied to spatially high-resolved data (~300m) from the Ocean and Land Colour Imager (OLCI) onboard the polar-orbiting satellites Sentinel-3.
In a next step we analyse the relationship between spatial variability metrics in the water vapour field and convective initiation over Germany, exploiting the advanced observation capabilities of current and future satellite-based imagers.
Thomas August (EUMETSAT) presents the current polar satellite sounders and makes a comparison with the capabilities of the future MTG infrared sounder
Satellite infrared sounders like IASI allow retrieving the vertical structure of the atmospheric humidity. Their measurements are exploited in synergy with the microwave (MW) sounders, when such companions are present on the same platforms as is the case in the operational EUMETSAT Polar System (EPS) programme and in the EPS-Second Generation (SG). This synergy increases the yield and quality of sounding in cloudy pixels. The future infrared sounder (IRS) onboard Meteosat Third Generation (MTG) will operate without MW companions. It will however provide unprecedented spatio-temporal sounding, with a typical ground-resolution of 7km and observations every 30 minutes over Europe.
The extensive utilisation of machine learning guarantees the provision of reliable atmospheric temperature and humidity profiles and uncertainty estimated within less than 30 minutes from sensing. We present here the characteristics of satellite thermodynamic profiles from the current and future missions and the experience made in studies with meteorological services to contribute to nowcasting severe weather events, and prepare to the future sounder missions.
Bryan Guarante (University of Wisconsin) uses a COMET course to explain the usefulness of analysing water vapour images with a goal of assessing the NWP fields.
In dynamically-active regions of the atmosphere, water vapour imagery approximates the same surface as the 1.5PVU height or pressure surface. Because of this, we can take advantage of the WV channels to find areas of mismatch between the NWP and the real atmosphere to adjust our synoptic scale forecasts.
Ivan Smiljanić (EUMETSAT) shows how the current MSG satellites can see low-level moisture and how does the moisture affect the weather.
High humidity in the air, close to the ground, could make you feel soggy in the summer but otherwise you won’t notice it. So why is it important to know all about it – is there a lot or very little moisture, where is it, what are dynamics of the moisture field? Well, moisture is really a key ingredient for many features in the atmosphere that can affect our daily lives to a high degree, from thunderstorm clouds to a fog or rime. In this session we will see how water vapour becomes a fuel for features in atmosphere to form, through a few real examples.
Hans Peter Roesli showcases the usefulness and characteristics of the 0.9 micrometer band channels, one of which will be available with MTG satellites.
At the time of refining the FCI requirements for nowcasting applications, numerical forecasts had much difficulty in handling low-level humidity (low-level forecasts rapidly dried with increasing forecast time). This was one of the reasons why the expert team for nowcasting proposed to add in MTG’s FCI.a solar water-vapour-absorbing in the 0.9-micron region (now NIR 0.914 micron) alongside the clear NIR 0.865 micron band. Although nowadays operational numerical models have overcome the moisture problem, NIR 0.914 might still find valuable applications, in particular when accounting for the frequent imaging of the same scene in daylight.
MODIS includes a clear NIR 0.8585 band and 3 bands in the 0.9-micron region: 0.936, 0.940 and 0.905 micron, with decreasing water vapour absorption. Selecting NIR 0.8585 and the weakest absorbing NIR0.905 as proxy bands for FCI some meteorological situations were investigated, where low-level humidity monitoring could have been beneficial to nowcasts. MODIS flying on Terra and Aqua usually deliver two daylight overflights of the same scene, which allows for a rough appreciation of evolution in time.
Gao&Kaufman (2003) discussed the MODIS bands in view of the MOD05/MYD05 products for Total Precipitable Water Vapour. Based on their paper MODIS imagery of the reflectivity ratio 0.905/0.8585 was produced as a proxy for FCI. Taking the ratio is simple and damps further the (minor) differences in background reflectivity between the two bands. It was found that the ratio generally varies between 0.6 (humid boundary layer) and (dry boundary layer), as already given by Gao&Kaufman.
Examples under clear European skies will show situations of old frontal zones, convergence lines or north foehn. A more complex situation of low-level moisture advection under cloudy skies over the Po Valley affords the frequent FCI imaging, in order to get the full picture of the moist-air advection.
Pieter Groenemeijer (ESSL) presents his findings in using low-level moisture proxy data from polar orbiting satellites at European Severe Storms Laboratory training events.
In preparation for MTG data, ESSL is carrying out a series of expert workshops and Testbeds in collaboration with EUMETSAT. At both event types, the increased capabilities of detecting low-level moisture from geostationary orbit, which the MTG program will enable, have received a high amount of attention. In our presentation, we will discuss a number of convective storm cases that were studied using proxy data from polar-orbiting instruments, such as MODIS. One of the ways to visualize low-level moisture is by depicting the ratio of the 0.91 and 0.85 μm channels with an intuitive color scale. We will discuss to what extent this and other proxies for low-level humidity can be used to anticipate the presence of a crucial ingredient for severe deep, moist convection...
Ivan Smiljanić (EUMETSAT) presents water vapour channels that will become available with the launch of the third generation of Meteosat satellites.
Water vapour molecules, i.e. a water gas in the atmosphere, absorbs radiation in different parts of spectrum. With present geostationary satellite, MSG, this fact is mostly utilised in the spectral region around 6 or 7 microns, i.e. in the Infra-red region. With the next generation of geostationary satellite, MTG, it will be possible to observe the processes of WV absorption in the solar part of the spectrum, namely around 900 and 1300 nm. A bit different processes of absorption, but also scattering are happening around those wavelengths – we will take a look what is exactly happening there, and how to utilise these processes to detect different features in the atmosphere.
Wilfried Jacobs (DWD) introduces the water vapour channels in the 2022 EUMeTrain Water Vapour Event Week.
The target group of this presentation is participants that are not familiar or do not feel familiar enough for understanding the presentations during the entire week. The first presentation deals with basics of vapour water channels in satellite products. First, the principle of radiation and radiation transfer will be outlined briefly and put in relation to wave lengths of imagers and vertical sounders by considering weighting functions. The second part deals with some examples by using single channels. Finally, corresponding composites (RGBs) and their applications will explained in detail.
The purpose of the lecture is to provide a necessarily brief overview of the basic physical principles underlying satellite precipitation estimation methods.
The estimation of precipitation from space was attempted almost at the beginning of the satellite meteorology era by establishing a somewhat loose link between visible and infrared imagery of cloud tops and precipitation intensity at the ground. Since the early days estimation methods have qualitatively and quantitatively evolved with the advent of passive microwave sensors first and precipitation and cloud radars more recently. The purpose of the lecture is to provide a necessarily brief overview of the basic physical principles underlying satellite precipitation estimation methods trying to make the audience aware of what the sensors actually “measure” (radiation properties) and how these measurements are converted into precipitation intensity. All the methods, either based on “passive” or “active” sensing, are necessarily indirect and thus a clear understanding of the physics of radiation and of cloud hydrometeors is needed for the correct use of the products. In fact, such understanding helps in identifying the limitations of the existing precipitation products, which are too often used improperly or taken for granted. The lecture will try to pave the way to the in depth lectures of the other instructors on more specific topics of the discipline.
Norman Wildmann presents a wind measurement technique based on the use of UAS, a.k.a. drones.
Exchange and transport processes in the ABL are driven by turbulence on a wide range of scales. Their adequate parameterization in numerical models is essential. In heterogenous and complex terrain, the common simplification of turbulence to statistical models does not necessarily hold. Coherent structures such as convective cells, gusts, slope and valley flows, but also turbulence in cities or behind wind turbines are features which are not well represented in models. A reason for the lack of understanding is the challenge to adequately sample their spatio-temporal structure. Small unmanned aerial systems (UAS, a.k.a. drones) are increasingly used to measure meteorological quantities, including the three-dimensional wind vector in the ABL. In this talk, methods and results will be shown how UAS, either fixed-wing or rotary-wing, can be used to obtain in-situ measurements and thus help to understand complex flows.
Ab Maas talks about the challenges that wind presents in ballooning.
Although balloons were by far the first manned aircrafts in the sky their economic and military importance stayed marginal.
The main reason for that is the difficulty of steering a balloon. Balloons go with the wind flow and the only way to steer a balloon is to find different wind directions at different heights. Therefore, wind and wind forecasts are of utmost importance for sport- and commercial ballooning.