Localized Heavy Rainfall Research Articles

Localized Heavy Rainfall Near Zoshigaya, Tokyo, Japan on 5 August 2008 Observed by X-band Polarimetric Radar - Preliminary Analysis -

Localized heavy rainfall that occurred in the Toshima, Chiyoda, Shinjuku, and Bunkyo wards of Tokyo, Japan on 5 August 2008, causing 5 deaths and the flooding of 34 houses above floor level, was observed by the National Research Institute for Earth Science and Disaster Prevention (NIED) X-band polarimetric radar (MP-X). Preliminary analyses of the radar data reveal the following characteristics of the rainfall event. Heavy rainfall occurred in a small area over a short period. The extents of the areas over which 1-hour accumulated rainfall was greater than 50 and 80 mm were about 20 and 5 km2, respectively. The maximum total rainfall amount (123 mm) from 11:30 to 13:30 LST was observed by MP-X over Edogawa Elementary School. The thunderstorm initially developed rapidly. Only 15 minutes after the onset of rainfall, a precipitation rate in excess of 100 mm h-1 was observed, continuing for 35 minutes from 11:55 to 12:30 LST. The maximum rainfall rate (153 mm h-1) was observed by a rain-gauge over Edogawa Elementary School at around 12:10 LST. A comparison of MP-X data with surface rain-gauge data reveals that MP-X provides more accurate rainfall information than conventional radar, making it useful in monitoring localized heavy rainfall.

Assimilation of Nationwide and Global GPS PWV Data for a Heavy Rain Event on 28 July 2008 in Hokuriku and Kinki, Japan

On 28 July, 2008, a local heavy rainfall occurred over the Hokuriku and Kinki districts, in central Japan. A stationary front existed near the heavy rainfall areas, and the atmospheric instability was increased by the inflow of the upper-level cold air. The operational mesoscale model (MSM) of the Japan Meteorological Agency (JMA) could not predict the heavy rainfall. The comparison of distributions of precipitable water vapor (PWV) between the initial condition of the MSM and the Global Positioning System (GPS) revealed that the MSM initial condition underestimated water vapor in the heavy rainfall areas because of a positional lag of a low-level convergence zone. Data assimilation experiments of GPS-derived PWV were conducted with JMA’s mesoscale 4 dimensional variational assimilation system (Meso 4D-Var). The PWV derived from the nationwide ground GPS network (GPS Earth Observation NETwork: GEONET) improved both the northward position error of the low-level convergence zone and the forecast of the observed rainfall. Moreover, further improvements were obtained when the PWV derived from the GPS stations of the International GNSS Service in East Asia were added.

Impact of initial condition uncertainties on the predictability of heavy rainfall in the Mediterranean: a case study

AbstractThis study explores the predictability of a heavy rainfall event that struck North Africa on 9 and 10 November 2001. This case is a paradigm of Mediterranean extreme events characterized by the presence of a deep upper‐level trough associated with an intense cyclone which developed over the Western Mediterranean basin. Using the French non‐hydrostatic mesoscale model MESO‐NH, numerical experiments starting from various initial atmospheric states were conducted to assess the impact of initial condition uncertainties on the precipitation and cloud cover forecast. To generate a set of perturbed atmospheric states, a simple date‐shifting initialization method was used. Two sets of simulations were run, using lateral boundaries and initial conditions derived from both the French operational global assimilation system Action de Recherche Petite Echelle Grande Echelle (ARPEGE) and the European Centre for Medium‐Range Weather Forecasts (ECMWF) system. Initial perturbations applied to the upper‐level trough propagated and intensified throughout the simulation, leading to some discrepancy in the forecast of the low‐level cyclone. While it was found that the upper‐level trough and the surface cyclone controlled the location of the overall precipitation pattern, the predictability of smaller‐scale features such as localized heavy rainfall was directly related to specific mesoscale structures. The low‐level jet associated with the surface cyclone and the location and the intensity of the surface‐low both impact upon the triggering and the sustainment of the convective cells. In consequence, small‐scale perturbations of these mesoscale features led to large errors in the precipitation forecast, especially in the Algiers area. Copyright © 2008 Royal Meteorological Society

Mesoscale simulation of an extreme rainfall event over Mumbai, India, using a high‐resolution MM5 model

AbstractMesoscale models are essential for the accurate prediction of high‐impact weather, such as severe thunderstorms, heavy rainfall events, mountain weather forecasting, cloudbursts and cyclones. An attempt has been made in the present study to simulate the heavy rainfall event that occurred during 26 July 2005 over Santa Cruz (19.20°N, 72.53°E) in Mumbai, India, using the Fifth‐Generation NCAR/Penn State Mesoscale Model (MM5). The cloud‐resolving mesoscale model with the right combination of the nesting domains, horizontal resolution and cloud parameterization schemes, is able to simulate the heavy rainfall event both qualitatively and quantitatively. The model results indicate the existence of an intense mesoscale vortex in the mid‐troposphere during this heavy rainfall event. The localized heavy rainfall which occurred over Santa Cruz may possibly be due to the subsidence of the mid‐tropospheric mesoscale vortex, superimposed on the active monsoon conditions over this region. Copyright © 2007 Royal Meteorological Society

Synoptic features of orographically enhanced heavy rainfall on the east coast of Korea associated with Typhoon Rusa (2002)

A record‐breaking heavy rainfall event, with a 24‐hr accumulated rainfall of 870.5 mm, occurred in a coastal area at the foot of a mountain range in the central‐eastern part of the Korean Peninsula during the passage of Typhoon Rusa (2002). Synoptic features of this case were investigated via high‐resolution numerical analysis and forecast fields obtained from the PSU/NCAR MM5. The main causes of this localized heavy rainfall include: 1) strong low‐level convergence of moist air from the sea into the coastal/mountainous area; 2) consequent orographic lifting; 3) low levels of lifting condensation and free convection; and 4) release of potential instability by orographic lifting to trigger deep convection.

Tropical cyclone triggering of sediment discharge in Taiwan

The impact of tropical cyclones on precipitation variability and surface processes in Taiwan is studied using suspended sediment and river discharge data along with a meteorological model of tropical cyclone dynamics. The interactions between tropical cyclones and topography produce distinctive, localized patterns of heavy precipitation that can trigger high sediment discharge in Taiwan's rivers. We focus on Typhoon Toraji, which made landfall in Taiwan on 30 July 2001 and was the first major tropical cyclone to affect Taiwan after the 1999 Chichi earthquake. The passage of the tropical cyclone eye over the east coast of Taiwan produced intense rainfall (>100 mm h−1) for a short period (about 2 hours), triggering the highest sediment concentration ever recorded on the Hualien River. Orographic effects localized heavy rainfall (between 10 and 50 mm h−1) over the southwestern slopes of the Central Mountain Range, triggering high sediment discharge on the Kaoping River and flushing landslide debris produced during the Chichi earthquake into the Choshui River. We show that a range of atmospheric processes, with distinctive spatial variability and varying degrees of coupling to topography, interacted with tectonic processes of limited spatial extent to produce the overall sediment discharge from Taiwan during Typhoon Toraji. Landscape evolution models may need to be modified to account for the distinctive patterns of localized rainfall in tropical mountain belts. Furthermore, the links between tropical cyclones and topography suggest the potential for a range of previously unrecognized feedbacks between tectonics and climate in tropical mountain belts.

Debris disasters caused by local heavy rainfall in Niigata area in July 2004 (prompt report)

Debris disasters caused by local heavy rainfall in Niigata area in July 2004 (prompt report)

Case Study of an Unusually Heavy Rain Event over Eastern Taiwan during the Mei-Yu Season

Abstract A heavy rain event during the mei-yu season was observed over eastern Taiwan on 28 May 2001 under a potentially unstable environment with high CAPE and copious moisture. This event, with an unusually high daily rainfall maximum of 307 mm, was observed in the Ilan area over northeastern Taiwan. The retrogression of a mei-yu front over the nearby ocean collocated with a short-wave trough provided favorable large-scale conditions for the production of localized heavy rainfall. Latent heating was suggested to be responsible for the retrogression and the development of the mei-yu front over the nearby ocean to the east of Taiwan. In addition to the large-scale forcings, the local circulations and local topography modulated the rainfall distribution over the Ilan area. During the daytime hours, the strengthened onshore wind component due to the intensified mei-yu frontal circulation and orographic lifting provided enhanced rising motion over the windward slopes of the mountain to produce the significan...

River backflooding into a karst resurgence (Loiret, France)

The group of springs located in the west part of the Val d'Orléans exemplifies a type of karstic emergence which has the particularity to get most of its recharge water from a single surface water source, which in this particular case is the River Loire. Hence the flow of this group of springs is known to fluctuate in a close relationship with the water level of the River Loire. Since the second half of the 1990s, the conduit of the upstream spring of the Loiret river (so-called Le Bouillon) has been periodically seen to be invaded by the turbid waters of a small surface tributary (Le Dhuy) flowing back from the confluence to the spring, which then functioned as a swallow-hole. Plotted in a Dhuy versus River Loire diagram, stages of backflooding days describe a domain limited by a curve of the form HDhuy= c+e ( aH Loire+ b) . The exponential form of the relation corresponds to the increasing resistance of the emerging flow of the spring to the backflooding of the tributary waters, as the River Loire stages rise. The equation above was used to compute a daily backflow index enabling the effective reconstruction of all occurrences effectively counted during the regular period of observation of the spring. Extended to 1985, one can observe that the early 1990s do not appear as a favorable period to backflow events but some may have occurred during the years 1986 to 1989. The observation of rainfall intensity preceding backflooding shows that in a short time span there is no necessity to evoke intrinsic changes inside the Val d'Orléans basin to explain what might appear as a troublesome new phenomenon. In conclusion backflooding has probably existed for a long time and is simply under the control of local heavy rainfall during low River Loire stages.

Factors controlling hypolimnetic ammonia accumulation in a lake

The factors controlling the degree of hypolimnetic ammonia accumulation in Lake Onogawa are discussed based on periodic observations since 1993. The standing stock of ammonia in the bottom 9 m of the water column was a good measurement for determining the extent of the hypolimnetic ammonia accumulation. It varied threefold from 144 mmol m−2 in 1998 to 429 mmol m−2 in 1996. The correlation between the annual maxima of the ammonia standing stocks and the annual maxima of the thickness of anoxic layers was significant at P = 0.01. This fact suggests that the degree of development of the anoxic layer is the primary factor controlling the extent of hypolimnetic ammonia accumulation. Sporadic local heavy rainfalls in 1998 perturbed the water column, and the formation of the anoxic layer was postponed more than one month, resulting in a lower level of hypolimnetic ammonia accumulation in 1998. A thick mineral deposit apparently formed during the local heavy rainfall and seemed to enclose the freshly deposited organic matter, which might be an effective source material of the hypolimnetic ammonia, and resulted in a low level of ammonia accumulation in 1999. By 2000, the lake seems to have recovered from the perturbation, suggesting that the major part of the hypolimnetic ammonia is derived from fresh organic matter deposited within a year.

Perturbations of a water column of Lake Onogawa by local heavy rainfall

The perturbations of a water column at the deepest part of Lake Onogawa by a local heavy rainfall were analyzed. Mixing throughout the water column (18.8-m deep) was indicated by changes in the distribution of water temperature. This mixing perturbed the hypolimnetic seasonal distributions of dissolved components. All partic-ulate components peaked at 10 m, suggesting a center of inflowing water. Compared with background levels, particulate nitrogen (PN), particulate carbon (PC), particulate phosphorus (PP), and suspended solids (SS) increased from 16-fold for PN to 100-fold for SS. Soluble reactive phosphorus was the only dissolved component that formed a clear maximum at 10 m, as did the particulate components. Assuming that SS consists mainly of mineral particles, SS can be classified into three categories: (1) A rapidly sinking fraction, the main body of the loaded SS, with a sinking rate exceeding 1 m day−1 and radii exceeding 2–3 μm. (2) A slowly sinking fraction with a sinking speed of about 10 cm day−1 and radii of 0.7–0.9 μm; this fraction is calculated to be about 4% of the total loaded SS at most. (3) A fraction that was essentially retained in the water column. The maximum estimate of this fraction was 0.5% of the total.

TEMPORAL FLUCTUATIONS OF HEAVY RAINFALL MAGNITUDES IN NEW ORLEANS, LOUISIANA: 1871–19911

ABSTRACT: Recent occurrences of heavy rainfall in New Orleans, Louisiana, have led to speculation that the local heavy rainfall regime has changed. To objectively determine the validity of these speculations, changing magnitudes of storm rainfall were investigated through an examination of the annual maximum storm series from 1871 to 1991 at the New Federal site. Although a long‐term trend was not found, the Wilcoxon test indicated that magnitudes during the last 14 years (from 1978–1991) differed significantly from the rest of the series.

守山市観測井における地球化学的研究

Between July 1985 and December 1986 we measured electrical conductivity, water-temperatures at different depths, and flow rate of the water of Moriyama hot spring in Shiga Prefecture. At the estuary of the old Yasu River near the eastern side of Biwako-Ohashi the observation well was drilled up to 1000m depth. Continuous measurements were also made of the chemical compositions of the bubble gas emanated from the hot spring. These data were carefully compared with the water level data of Lake Biwa and the meteoric factors, to check any possible relationship. During the observation period, the flow rate, the water-temperatures and the chemical compositions of the bubble gas anomalously changed twice. The first one can be the precursor to the earthquake of M5.0, which occurred on October 3, 1985 near the Hanaore fault. However, the second one is considered to be caused by the local heavy rainfall on July 22, 1986.

Mechanism of slope failure during heavy rainfall in Nagasaki, July 1982 : Iseda, T; Tanabashi, I Natural Disaster SciV8, N1, 1986 P55–84

On July 23, 1982, 299 human lives were lost in Nagasaki prefecture due to sediment disasters such as landslides, rockfalls and debris flows caused by localized heavy rainfall. So it is important to clarify a mechanism of slope failure during heavy rainfall for sediment disaster prevention. In this paper a model experiment of slope failure due to water infiltration is carried out and the phenomenon of progressive failure of slope is observed. A finite element analysis is then applied to two cases of failed slope in Nagasaki City. This is divided into two stages, a saturated-unsaturated seepage flow analysis and a stability analysis taking into account the seepage force and the reduction of strength due to the rise in the degree of saturation. Their failure under the conditions of preceding rainfall on the day of failure, topography, geology and so on is also checked. A mechanism of slope failure during heavy rainfall has been identified. The article also demonstrates that slope failure can be predicted if a rise in the groundwater table can be detected. (TRRL)

Investigation and Repair of Tectonic and Storm-Related Road Damage near the Garlock Fault, California

Major damage to the Randsburg Wash Test Range Access Road at the Naval Weapons Center occurred during a thunderstorm the night of August 18, 1983. The damage occurred within zones of weakness related to tectonic strain accumulation across the nearby Garlock fault. Two zones of surface cracking and Assuring, one 732 m long and the other 686 m long, intersect the road. The primary damage, largely erosional, included open fissures up to 30 cm wide, and open and collapsed tunnels with cross-sectional dimensions of 1 to 2 m. Repair of the road involved four major considerations: (1) open fissures extending to an unknown depth, (2) continuing tectonic strain accumulation, (3) localized heavy rainfall and flash flooding, and (4) maintaining the road in a safe and usable condition. These considerations required the incorporation of somewhat novel, non-standard repair techniques. The road repair involved extensive exploratory excavation and engineered backfilling. About 900 m3 of material were excavated to an average depth of 4 m. The stratigraphy included up to 0.7 m of unconsolidated silty sand underlain by 3 m of plastic lacustrine clay and an unknown thickness of coarse, unconsolidated, uniformly graded sand. These materials were replaced by engineered fills designed to: prevent erosion of the subgrade; bridge or collapse into cracks or fissures that may develop; prevent or diminish the effects of reflection cracking; allow drainage; and accommodate tectonic strain. The road-shoulder backfill consisted of 1.5 m of a compacted mixture of arkose and the previously excavated clay overlain by 3.5 m of compacted arkose. The road backfill included a basal, 0.5-m-thick layer of cobbles, an overlying 0.5-m-thick layer of compacted, 19 mm concrete aggregate and 4.5 m of compacted decomposed granite.

Local Heavy Rainfall in Isahaya Area

Local Heavy Rainfall in Isahaya Area

The Local Heavy Rainfall in Niigata Prefecture on the 12th to 14th July 1960

An unusually heavy rainfall occurred in Niigata Prefecture, on the 12th to the 14th of July, 1960. According to the author's analysis using synoptic charts, the rain was caused by the stagnation of a warm front corresponding to the Jet stream over Akita to Sendai, A moist tongue of isodrosotherms extended from northwest to southeast across Honsyu in the shape of an arc carried by the strong wind around the high pressure belt. The type of the rainfall indicates the occurrence of an extremely unstable atmospheric condition which brought about this unusual weather.

Rainfall distribution over Delhi State during monsoon

Based on the data for the period 1939-1954, the mean values of rainfall and number of rainy days during the, monsoon season at the various raingauge stations as well as the extreme values of these have been given; spatial distribution of heavy, rainfall over the State and the incidence of heavy rainfall at the various location have been studied. From a study of the synoptic charts on days prior to the days on which local heavy rainfall over was reported, an attempt has been made to indicate the topical synoptic situations which usually lead to local heavy rainfall over Delhi State during the next 24hours.Typical situation ‘have been illustrated by charts.

停滞前線附近における局地性豪雨の発生について

梅雨末期の豪雨をPPIレーダーの写真と雨量図について比較して局地的に降る豪雨の申で局地に集中して降る豪雨の一つの典型とみなされる例を示す.1957年7月上旬の脊振山のレーダーの観測(福岡管区気象台でレーダーを予報に応用する研究の一環として行われた)に基いて解析した結果 (1)低層の南西jet気流(2)暖域内の対流不安定の成熟が定着性レインバンドの発生,発達の主な原因であることがわかつた。また,自記雨量観測点ではこまかい等雨量線の模様が引けないので区内観測所の資料を用いて細かい日雨量パターンを引いてみたところ前線と定着性レインバンドの近くにその交点附近で狭いが非常に強い降雨域があることとわかつた。従つてこれら二つの結果は上述の二つの条件が前線の定常化は局地性の豪雨の予報にとつて非常に重要な要因であつたことを暗示している。