Dual-polarization radar often detects columnar regions of enhanced differential reflectivity (ZDR) extending vertically above the environmental 0 °C level. Indicative of supercooled liquid drops and ...wet ice particles lofted by strong updrafts, these ZDR columns are increasingly understood to be of use in predicting extreme rainfall. With the aim of achieving practical application of ZDR column measurements, this paper focuses on the relationship between the height of ZDR columns and rainfall intensity near the ground.All the data on ZDR columns analyzed in this study was collected from weather radar stations in Japan. The height of each column and rainfall rates at low levels were analyzed using an automated algorithm. A regression analysis result reveals peak column height to be positively correlated with maximum rainfall rate near ground level, and that rainfall intensity on the ground is likely to exceed 50 mm h−1 when radar identifies a ZDR column. Furthermore, extreme rainfall with an intensity of 180 mm h−1 or more is likely associated with a column over 3 km tall from the 0 °C level. These findings suggest that surveillance of ZDR columns can contribute to the reliability of very short-range forecasts or nowcasts as well as assist with the issue of early warnings of extreme rainfall and flash floods.
Based on three-dimensional lightning locations and S-band polarimetric Doppler radar data, a hailstorm that occurred on Hainan Island on June 4, 2021 was analyzed in detail. The analysis revealed ...that the flash activity of hailstorms is mainly intracloud (IC) flashes, the cloud-to-ground (CG) flashes frequency were less, positive CG flashes (+CG) were domination in the CG activity before hailfall. The flash frequency appeared “lightning jumps” when hailstorms merging with convective cells, ice hydrometeors also rapidly increased in the clouds of the mixed-phase area in this period, which was beneficial for efficient electrification. The Zdr column and evolution of echo top indicated presence of an intense updraft during the mature stage of the hailstorm. Zdr column depth about 4 km close to 20 °C during the mature stage. Near the time of the hailfall, Zdr column was contraction, due to sinking hail generated downdraft within the cloud. Zdr column after hailfall may be produced by the convergence of downdraft and sea breeze. In combination with the spatiotemporal distribution of the hydrometeors in hailstorms, flash activity was most closely related to graupel and it plays a important role for flashes electrification. The hail plays a minimum role in charge separation. Radiation sources were concentrated between 50 dBZ and 55 dBZ. The spatial distribution of radiation sources indicated possible complex charge structure within hail storm clouds.
•This article firstly used data of 3D lightning location on Hainan Island to analyze hailstorm process.•This article analyzes the dynamical characteristics within the cloud through Zdr columns. Zdr column after hailfall may be produced by the convergence of downdraft and sea breeze.•This article used algorithm of fuzzy logical classification to infer hydrometeors within cloud. And analyzing relationship between total flashes and hydrometeors of hailstorm during life-cycle of hailstorm.
Surface raindrop size distributions over a rain shadow region during the Indian summer monsoon are clustered using the k‐means algorithm. The rainfall for five dominant clusters has distinct vertical ...features in polarimetric radar and micro rain radar. The deep convection with low cloud bases and high liquid water is associated with sharply increasing radar reflectivity at low levels and the largest drops at the surface. The large drops, originated by ice processes, break while falling below the melting layer, causing a peak in raindrops smaller than 0.5 mm diameter near the cloud base, where the falling raindrops rapidly grow by collision‐coalescence without breaking. The number concentration in the stratiform rain is relatively moderate; hence a gradual raindrop growth, and uniform vertical reflectivity. However, few raindrops in stratiform rain grow to a larger diameter than in convective rain, for the same rain rate due to the absence of collisional breakup.
Plain Language Summary
Different clouds produce raindrops of various sizes in different concentrations. Therefore, we classified ground‐based measurements of raindrop sizes to study the rainfall characteristics during the monsoon. Generally, raindrops grow inside the cloud as they collide and combine with smaller drops, and break when they collide with larger drops. These processes affect the rain intensity and the sizes of raindrops. We found the abundance of tiny raindrops in convective clouds at lower levels. The larger drops collect them and grow while falling from this region of the cloud. The concentration of the tiny drops is higher when the cloud is taller and the cloud base is lower with sufficient water. The growing raindrops are detected by the radar with an increasing reflectivity signal. On the other hand, stratiform rain has a lower concentration of raindrops and less water. Therefore, the raindrop growth is slow, and the radar reflectivity generally appears uniform from cloud to ground. Despite this, due to a low concentration of large drops in the stratiform cloud, some raindrops gradually grow without breaking. Therefore, larger raindrops are often found in stratiform rain than convective rain, for the same rain intensity.
Key Points
Five drop size distribution clusters at the surface during the Indian monsoon have distinct rainfall features in polarimetric radar and micro rain radar
A low‐level peak in tiny drops helps collisional growth of raindrops in convective rain, increasing the radar reflectivity downwards
Raindrop growth is strong in deep convection with low cloud base and high liquid water but weak in stratiform rain due to low drop density
In the San Francisco Bay Area, precipitation occurs in the wintertime, mostly as rain. Wintertime rainfall can be further classified into cold or stratiform rain with a typical radar bright band (BB) ...signature and warm orographic rain with the absence of a radar BB. Vertical pointing S-band profiler radar and disdrometer measurements from two of National Oceanic and Atmospheric Administration (NOAA)'s hydrometeorology testbed (HMT) sites in California are used to study the differences in microphysical properties between these two types of rain and their implications in radar rainfall estimation. A methodology has been developed to discriminate nonbright band (NBB) rainfall from BB rainfall using reflectivity (Z) and differential reflectivity (<inline-formula> <tex-math notation="LaTeX">Z_{\mathrm { DR}} </tex-math></inline-formula>) computed from disdrometer data. Delineating the two rainfall types in this way allowed for an algorithm to be applied to the radar scans to identify rainfall types and apply appropriate reflectivity-based and specific differential phase (<inline-formula> <tex-math notation="LaTeX">K_{\mathrm { DP}} </tex-math></inline-formula>)-based rainfall estimators. Recently, a gap-filling X-band weather radar with dual-polarization capabilities was deployed in the San Francisco Bay Area in Santa Rosa to aid in weather monitoring and provide high-resolution quantitative precipitation estimation (QPE) products. When applied to real radar observations, this method shows great potential for improving the QPE compared to traditional operational products which more often tend to underestimate rainfall in the California coastal region.
Nucleotide-binding leucine-rich repeat (NB-LRR, or NLR) receptors mediate pathogen recognition. The Arabidopsis thaliana NLR RPP1 recognizes the tandem WY-domain effector ATR1 from the oomycete ...Hyaloperonospora arabidopsidis through direct association with C-terminal LRRs.
We isolated and characterized homologous NLR genes RPP1-EstA and RPP1-ZdrA from two Arabidopsis ecotypes, Estland (Est-1) and Zdarec (Zdr-1), responsible for recognizing a novel spectrum of ATR1 alleles.
RPP1-EstA and -ZdrA encode nearly identical NLRs that are phylogenetically distinct from known immunity-activating RPP1 homologs and possess greatly expanded LRR domains. Site-directed mutagenesis and truncation analysis of ATR1 suggests that these homologs recognize a novel surface of the 2nd WY domain of ATR1, partially specified by a C-terminal region of the LRR domain. Synteny comparison with RPP1 loci involved in hybrid incompatibility suggests that these functions evolved independently.
Closely related RPP1 homologs have diversified their recognition spectra through LRR expansion and sequence variation, allowing them to detect multiple surfaces of the same pathogen effector. Engineering NLR receptor specificity may require a similar combination of repeat expansion and tailored amino acid variation.
To gain a deeper understanding of the formation and evolutionary mechanisms of a bow-shaped squall line (BSL) that occurred in East China on 10 May 2021, observations from S-band dual-polarization ...radars, a disdrometer and other instruments are used to investigate the characteristics and evolution of the kinematic, microphysical and radar echo structure within the squall line during its formative and mature stages. The results are as follows. The updraft induced by upper-level divergence and vertical thermal instability induced by the cold source at the middle and top of the troposphere provided environmental conditions suitable for the formation and strengthening of a squall line. The characteristics of the vertical vorticity at the leading edge of the squall line provided a good indication of its echo structure and evolutionary trend. The mechanism behind a new echo phenomenon—double high-differential reflectivity (ZDR) bands—observed in plan position indicator scans produced by the dual-polarization radar is investigated from the kinematic and microphysical structural perspectives. The evolutionary characteristics of the microphysical structure of the bulk of the squall line and its trailing stratiform cloud region are analyzed based on the quasi-vertical profiles retrieved from the S-band dual-polarization radar in Quzhou. Moreover, a conceptual model describing this type of BSL with a trailing region of stratiform rain in the warm sector is developed to provide technical support for the monitoring and early warning of BSLs.
A 10 Gb/s PAM-4 transmitter (TX) with a modulo-based equalization technique is presented. The proposed feed-forward Tomlinson-Harashima precoding (FF-THP) scheme takes advantage of both ...Tomlinson-Harashima precoding (THP) and feed-forward equalization (FFE). The vertical eye margin (VEM) is enhanced by removing the precursor inter-symbol interference (ISI) with pretaps while incorporating the modulo operation. The VEMs of equalization methods are derived based on z-domain response (ZDR). The effectiveness of the FF-THP is examined by quantitative analysis and numerical simulation. Especially for a one-pole channel with a precursor, optimized tap coefficients of an FFE and an FF-THP are derived as closed-form concerning the precursor and the first postcursor. Calculations of decision threshold voltage and estimated bathtub curve based on Gaussian noise are featured by using the histogram of an eye diagram. The advantages of the FF-THP over a conventional FFE are measured by a fabricated chip. The proposed TX compensates for a 21 dB channel loss with a level mismatch ratio of 99.1% and with a figure of merit (energy efficiency per sum of channel ISI) of 4.05 pJ/b/ISI. Moreover, the FF-THP achieves 38% and 87.5% improvement on VEM and horizontal eye margin, respectively, compared with an FFE. It is fabricated in 28 nm CMOS technology, occupying an active area of 0.075 mm 2 .