Satellite skills and knowledge for operational meteorologist

Polar Lows are generally characterized by severe weather in form of strong winds, snow showers sometimes even hail, which sometimes results in loss of lives, especially on the sea. Sometimes these systems are also connected with the term Arctic Hurricane, which had been used for especially intense Polar lows. Compromising definition of Polar low is: small, but fairly intense low in northern maritime regions.

The polar lows are formed in cold air outbreaks, north of the polar front, mostly in the regions east of 0°E and south of 75°N. Favorable season for them is the cold part of the year. By size, they are smaller (200-600 km) than ordinary synoptic lows with life-span typically around 18 hours, and with very intense change of weather.

Why was it difficult to forecast polar lows and what are the improvements in that area since 2000? In my presentation I will also show you how we are forecasting Polar lows, which models we are using and of course satellite products.

Go to webcast

Lecture slides

Commas are meso-scale structures developing within cold air, that can cause severe weather on the ground, often behind frontal cloud bands. They occur mainly during the cold season and are a common feature for Northern and Western Europe - nevertheless commas can also be found in the south. In this lecture life cycles and the appearance of commas in satellite imagery will be demonstrated. Different types of development exist - Within the cold air commas can grow out of EC starting as a small feature which is growing in to the typical meso-scale cloud spiral. On the other hand commas can be found in connection with occlusion when they split off the cloud spiral and become a separate feature on their own. Typical weather events are storms and heavy precipitation (in form of showers and thunderstorms). Examples of real cases will be shown and they shall illustrate the typical synoptic situations.

Go to webcast

Lecture slides

Precipitation within extratropical cyclones often organizes into mesoscale substructures known as precipitation bands. The purpose of this presentation is to better understand how precipitation organizes into bands. We will discuss about Shapiro-Keyser and the Norwegian models of cyclones, why do they form, the differences between them, also where in cyclones precipitation bands form, their structures and evolutions, what controls their locations and intensities, and techniques to diagnose precipitation bands. In the end we will discuss about occlusion bands and how do they actually form considering latest researches.

Go to webcast

In this second part of the Cyclogenesis and Occlusion Cloud Bands lecture, a special form of cyclogenesis is treated in detail: the “rapid cyclogenesis” which is connected with very severe and often catastrophic weather events.

All processes and weather systems are presented from the aspect of “Conceptual Model thinking”; that means the typical appearance in satellite images is connected to the physical background which is responsible for the cloud configurations; then these results are connected to relevant numerical parameters in horizontal and vertical presentation. And all of the presented CMs are connected to the typical connected weather events. This combination of different meteorological material is especially important in forecasting and nowcasting.

Go to webcast

Lecture slides

Cyclogenesis and occlusion cloud bands are common meteorological phenomena which are tightly connected. While “cyclogenesis” is a process, describing the development of a low centre, which can last from few hours to several days, the occlusion cloud bands are the result of this cyclogenesis process. Occlusion cloud bands differ from cold and warm front bands because of their history as well as their physical status.

The two lectures start from the classical cyclogenesis (occlusion) processes which are related to the classical polar front theory and introduce then the conveyor belt view of these processes culminating in the warm and cold conveyor belt occlusion types.

The occlusion cloud band types are described and compared to cold and warm front types in their horizontal as well as vertical depiction.

Also special subtypes of occlusion processes like “instant occlusion” and “cold air development” are mentioned.

Go to webcast

Lecture slides

When observing the development of frontal zones in satellite imagery, forecasters should always keep an eye on frontal sub-structures like upper waves, front intensifications or rapid cyclogenesis. It is important to look for frontal substructures, because they often show new developments. NWP models sometimes catch the situation, sometimes not. Especially for rapid or small scale developments, model performance may leave a lot to be desired.

Here we focus on comparison of model outputs and satellite data regarding frontal substructures. Because the data are easily compared and show great results, satellite images are a good tool for model output verification.

Go to webcast

Lecture slides

Fronts as described in the “Bergen school” by Vilhelm Bjerknes are early conceptual models. Parameters typical for the changing of air masses were named and used by forecasters to recognize transition zones (fronts) between air masses. Satellite information expressed how right Bjerknes was in his CM thinking, but this information showed also that fronts can have much more complicated structure and life cycle Bjerknes could imagine.

In SatManu there are 5 different types of cold- and 3 different types of warm fronts that are recognized and described.

In this lecture we concentrate on warm- and cold fronts and show how we can analyze them with help of CM thinking.

Go to webcast

Lecture slides

Getting a good, actual weather picture within short time is essential for a forecaster who has to react quickly and adequately on weather changing’s.

The huge amount of weather data which are available makes it almost impossible for a human being to handle. Thinking in conceptual models is the only way to deal with this problem

Meteorological satellites opened a whole new field in the conceptual model thinking in operational meteorology. Now there was an opportunity to recognize weather systems by detecting cloud patterns and verify this first guesses with observations and numerical parameters.

Within 20 years of the project fifty-three different conceptual models were described in a manual: Sat Manu. Also for the southern hemisphere, we have already fifteen CM’s described.

Go to webcast

Lecture slides

The presentation addresses some of the general impacts of the higher temporal and spatial resolution, available with the most recent or upcoming geostationary weather satellites. Main contribution of the higher scan frequency (of the order of 2.5 minutes or shorter) is in much better temporal coverage of evolution of rapidly developing weather systems, namely those associated with deep convection. The impact of shorter scan frequency will be demonstrated using data from the MSG 2.5-minute experiment. Spatial resolution affects not only the fidelity of imagery, but also (and more importantly) some of the quantitative characteristics of cloud tops - such as local cloud top brightness temperature minima, associated with overshooting tops. This effect will be demonstrated using high resolution polar satellite imagery.

Go to webcast

Lecture slides

Short-term Prediction Research and Transition (SPoRT) Center, part of the United States’ NASA program, has been a leader in transitioning total lightning observations to operational forecasters. This effort began in 2003 with a single, NASA-owned ground-based lightning mapping array. The effort has since expanded to include multiple networks supporting a variety of end users for severe weather, safety, and aviation. This effort serves as the foundation for preparing the United States forecaster community for the Geostationary Lightning Mapper (GLM) set to launch aboard GOES-R. This presentation will discuss the GLM and its observations, what total lightning is, and how these data can be used operationally based on ongoing activities to prepare the United States for GLM. The GLM instrument is very similar to the Meteosat Third Generation’s Lightning Imager and presents an opportunity for collaboration between U.S. and EUMETSAT forecasters.

Go to webcast

Lecture slides

EUMETSAT is currently developing with ESA the geostationary Meteosat Third Generation (MTG) satellite system to continue and enhance the service currently provided by Meteosat Second Generation (MSG), from 2020 onwards. One of the new missions of MTG is the Lightning Imager (LI) mission, which is intended to provide a real time lightning detection and location capability in support to nowcasting of high impact weather. The LI measures the total lightning, i.e. the combined cloud-to-ground and intracloud/cloud-to-cloud lightning. One of the major tasks in the MTG program is to provide the Level 2 product processor. The initial L2 products are based on the detection of the optical pulses on top of clouds following a false event filtering and clustering of the detected triggered lightning events in time and space. These are composed to the initial L2 products, i.e. groups and flashes representing geophysical flashes and strokes. A further L2 product category is the Accumulated Products, which integrate the Flash products into a fixed 2 km grid (same as for the MTG Flexible Combined Imager IR channels) with a 30 sec accumulation period. These 30-sec periods can be further stacked by users. The products are disseminated as short duration chunks in order to meet the timeliness requirements.

Go to webcast

Lecture slides

Major advancements of the MTG with respect to MSG are the superior resolution and the added 2.3 um channel, which in combination allow retrieving cloud particle effective radius and discerning cloud phase at the very high resolution of 500 m. These cloud properties determine whether a cloud would be precipitating, and if so whether it would be rain or snow. This information is particularly advantageous for observing small boundary layer clouds, which often produce rain showers in very clean air masses, such as at the Atlantic coast, but stop raining when polluted inland. This is also the case for post frontal clouds that may produce snow showers. It will be possible to detect it with the MTG.
The ability of retrieving high resolution cloud drop effective radius in convective clouds makes it possible to retrieve cloud drop concentrations, which are dominated by aerosol particle concentrations. The retrieved cloud drop concentrations can be reversed to infer the concentrations of particulate air pollution that occur under cloud decks that are rooted in the boundary layer. A proxy to the retrievals is an RGB color combination that can show the same qualitatively.
Furthermore, the inferred cloud drop concentrations has a predictive value for the nature of foretasted convective storms in that air mass, because the aerosols can invigorate the storms and make them more prone to producing lightning and hail.

Go to webcast

Lecture slides