Data Assimilation Enhancements to Air Force Weathers Land Information System

The United States Air Force (USAF) has a proud and storied tradition of enabling significant advancements in the area of characterizing and modeling land state information. 557th Weather Wing (557 WW; DoDs Executive Agent for Land Information) provides routine geospatial intelligence information to warfighters, planners, and decision makers at all echelons and services of the U.S. military, government and intelligence community. 557 WW and its predecessors have been home to the DoDs only operational regional and global land data analysis systems since January 1958. As a trusted partner since 2005, Air Force Weather (AFW) has relied on the Hydrological Sciences Laboratory at NASA/GSFC to lead the interagency scientific collaboration known as the Land Information System (LIS). LIS is an advanced software framework for high performance land surface modeling and data assimilation of geospatial intelligence (GEOINT) information

Evaluating pySTEPS optical flow algorithms for convection nowcasting over the Maritime Continent using satellite data

<jats:p>Abstract. The Maritime Continent (MC) regularly experiences powerful convective storms that produce intense rainfall, flooding and landslides, which numerical weather prediction models struggle to forecast. Nowcasting uses observations to make more accurate predictions of convective activity over short timescales (∼ 0–6 h). Optical flow algorithms are effective nowcasting methods as they are able to accurately track clouds across observed image series and predict forward trajectories. Optical flow is generally applied to weather radar observations; however, the radar coverage network over the MC is not complete and the signal cannot penetrate the high mountainous regions. In this research, we apply optical flow algorithms from the pySTEPS nowcasting library to satellite imagery to generate both deterministic and probabilistic nowcasts over the MC. The deterministic algorithm shows skill up to 4 h on spatial scales of 10 km and coarser and outperforms a persistence nowcast for all lead times. Lowest skill is observed over the mountainous regions during the early afternoon, and highest skill is seen during the night over the sea. A key feature of the probabilistic algorithm is its attempt to reduce uncertainty in the lifetime of small-scale convection. Composite analysis of 3 h lead time nowcasts, initialised in the morning and afternoon, produces reliable ensembles but with an under-dispersive distribution and produces area under the curve scores (i.e. ratio of hit rate to false alarm rate across all probability thresholds) of 0.80 and 0.71 over the sea and land, respectively. When directly comparing the two approaches, the probabilistic nowcast shows greater skill at ≤ 60 km spatial scales, whereas the deterministic nowcast shows greater skill at larger spatial scales ∼ 200 km. Overall, the results show promise for the use of pySTEPS and satellite retrievals as an operational nowcasting tool over the MC. </jats:p&gt

A Regulatory Role of the Bateman Domain of IMP Dehydrogenase in Adenylate Nucleotide Biosynthesis*

The Bateman domain (CBS subdomain) of IMP dehydrogenase (IMPDH), a rate-limiting enzyme of the de novo GMP biosynthesis, is evolutionarily conserved but has no established function. Deletion of the Bateman domain has no effect on the in vitro IMPDH activity. We report that in vivo deletion of the Bateman domain of IMPDH in Escherichia coli (guaBΔCBS) sensitizes the bacterium to growth arrest by adenosine and inosine. These nucleosides exert their growth inhibitory effect via a dramatic increase in the intracellular adenylate nucleotide pool, which results in the enhanced allosteric inhibition of PRPP synthetase and consequently a PRPP deficit. The ensuing starvation for pyrimidine nucleotides culminates in growth arrest. Thus, deletion of the Bateman domain of IMPDH derepresses the synthesis of AMP from IMP. The growth inhibitory effect of inosine can be rescued by second-site suppressor mutations in the genes responsible for the conversion of inosine to AMP (gsk, purA, and purB) as well as by the prsA1 allele, which encodes a PRPP synthetase that is insensitive to allosteric inhibition by adenylate nucleotides. Importantly, the guaBΔCBS phenotype can be complemented in trans by a mutant guaB allele, which encodes a catalytically disabled IMPDHC305A protein containing an intact Bateman domain. We conclude that the Bateman domain of IMPDH is a negative trans-regulator of adenylate nucleotide synthesis, and that this role is independent of the catalytic function of IMPDH in the de novo GMP biosynthesis