How organized is deep convection over Germany?

Abstract

Deep moist convection shows a tendency to organize into mesoscale structures. To be able to understand the potential effect of convective organization on the climate, one needs first to characterize organization. In this study, we systematically characterize the organizational state of convection over Germany based on two years of cloud-top observations derived from the Meteosat Second Generation satellite and of precipitation cores detected by the German C-band radar network. The organizational state of convection is characterized by commonly employed organization indices, which are mostly based on the object numbers, sizes and nearest-neighbour distances. According to the organization index org , cloud tops and precipitation cores are found to be in an organized state for 69% and 92% of the time, respectively. There is an increase in rainfall when the number of objects and their sizes increase, independently of the organizational state. Case-studies of specific days suggest that convectively organized states correspond to either local multi-cell clusters, with less numerous, larger objects close to each other, or to scattered clusters, with more numerous, smaller organized objects spread out over the domain. For those days, simulations are performed with the large-eddy model ICON with grid spacings of 625, 312 and 156 m. Although the model underestimates rainfall and shows a too large cold cloud coverage, the organizational state is reasonably well represented without significant differences between the grid spacings. K E Y W O R D Sconvective organization, ICON model, organization indices, model evaluation

Mesoscale marine tropical precipitation varies independently from the spatial arrangement of its convective cells

“…Pscheidt et al . () also suggested a potential poor correlation between organization and precipitation by looking at simulations, radar and satellite observations over Germany.…”

Assessing Convective Organization in Tropical Radar Observations

“…These indices take as input a two‐dimensional binary field representing a set of “convective objects” within the domain of interest, and they output a scalar value that measures the extent to which the convection may be considered to be “organized.” SCAI and COP were developed based on satellite‐derived cloud distributions and I org was developed based on distributions of updrafts in simulations, but in principle, they can be applied to any two‐dimensional binary field. For example, they have recently been calculated for radar observations in Cheng et al () and Pscheidt et al ().…”

“…SCAI and COP were developed based on satellite-derived cloud distributions and I org was developed based on distributions of updrafts in simulations, but in principle, they can be applied to any two-dimensional binary field. For example, they have recently been calculated for radar observations in Cheng et al (2018) and Pscheidt et al (2019). SCAI considers the number of convective objects and the distances between their centroids, whereas I org compares the distribution of convective objects to the distribution that would result from a random placement of convective objects.…”

Impact of resolution and air temperature on Large Eddy Simulation of mid-latitude summer time convection

“…To investigate whether convective clouds tend to organize in space, we follow the approach used in Pscheidt et al (2019):…”

“…I org is defined as the area below such a comparison curve (for more details see e.g. Pscheidt et al, 2019;Tompkins and Semie, 2017). From the 100 computed I org indices we select the 2.5th and 97.5th percentiles to identify the spatial distribution.…”