Showing papers on "Precipitation published in 1991"

Amazonian Deforestation and Regional Climate Change

Abstract: Large-scale conversion of tropical forests into pastures or annual crops could lead to changes in the climate. We have used a coupled numerical model of the global atmosphere and biosphere (Center for Ocean-Land- Atmosphere GCM) to assess the effects of Amazonian deforestation on the regional and global climate. We found that when the Amazonian tropical forests were replaced by degraded grass (pasture) in the model, there was a significant increase in the mean surface temperature (about 2.5°C) and a decrease in the annual evapo-transpiration (30% reduction), precipitation (25% reduction), and runoff (20% reduction) in the region. The differences between the two simulations were greatest during the dry season. The deforested case was associated with larger diurnal fluctuations of surface temperature and vapor pressure deficit; such effects have been observed in existing deforested arms in Amazonia. The calculated reduction in precipitation was larger than the calculated decrease in evapotranspirat...

Surface Climate and Streamflow Variability in the Western United States and Their Relationship to Large‐Scale Circulation Indices

Abstract: A statistical analysis was undertaken to determine the nature and magnitude of the relationship of precipitation, temperature and streamflow in the western United States to large-scale atmospheric circulation patterns. The Southern Oscillation Index (SOI) was used as an indicator of the El Nino/Southern Oscillation (ENSO) and the PNA index as an indicator of the Pacific//North America pattern. These indices were correlated with surface climate data and split sample analyses were conducted to determine climate response during the extreme phases of each index. October–March precipitation was shown to be most strongly correlated with SOI averaged over the July–November period. The analysis showed that there are two centers of opposite association with the SOI. During low values of the SOI (ENSO events) precipitation is low in the Pacific northwest and high in the desert southwest. Correlations between SOI and temperature were greatest in the Pacific northwest. The split sample analysis also revealed statistically significant differences in precipitation occurring during extremes of the SOI. The PNA pattern was related to precipitation and temperature over a concurrent time period. Especially strong associations were noted in the Pacific northwest for both precipitation and temperature. Streamflow showed associations with SOI similar to precipitation.

Differential utilization of summer rains by desert plants

Abstract: Seasonal changes in the hydrogen isotope ratios of xylem waters were measured to determine water sources used for growth in desert plants of southern Utah. While all species used winter-spring recharge precipitation for spring growth, utilization of summer rains was life-form dependent. Annuals and succulent perennials exhibited a complete dependence on summer precipitation. Herbaceous and woody perennial species simultaneously utilized both summer precipitation and remaining winter-spring precipitation, with herbaceous species much more reliant on the summer precipitation component. Several of the woody perennials exhibited no response to summer precipitation. Currently, precipitation in southern Utah is evenly partitioned between winter and summer time periods; however, global circulation models predict that summer precipitation will increase in response to anticipated climate change. Our data indicate that components within the community will differentially responde to the change in precipitation patterns. These results are discussed in relation to impact on competition and possible changes in community structure.

New precipitation and accumulation maps for Greenland

Abstract: Annual total precipitation and the annual accumulation on the Greenland ice sheet are evaluated and presented in two maps The maps are based on accumulation measurements of 251 pits and cores obtained from the upper accumulation zone and precipitation measurements made at 35 meteorological stations in the coastal region To construct the accumulation map, the annual precipitation was split into solid and liquid precipitation components Annual total precipitation exceeding 2500mmwe occurs on the southeastern tip of Greenland, while the minimum precipitation is estimated to occur on the northeastern slope of the ice sheet The mean annual precipitation for all of Greenland is 340 mm we The largest annual accumulation of about 1500 mm we is found on the glaciers in the southeastern corner of Greenland, while the smallest accumulation is found on the northeastern slope of the ice sheet west of Danmarkshavn The mean accumulation on the Greenland ice sheet is estimated at 310mmwe The regional difference in accumulation is examined with respect to the 850hPa(mbar) level circulation The present surface topography is found to play an important role in determining regional accumulation on the ice sheet

Diurnal Variability of the Hydrologic Cycle in a General Circulation Model

Abstract: In the present Colorado State University GCM simulation-based analysis of the diurnal and semidiurnal variability of precipitation, precipitable water, evaporation, cloudiness, horizontal moisture flux convergence, and cloud radiative forcing, a realistic afternoon precipitation maximum is obtained over land in warm rainy regions, as well as an early morning maximum over the oceans. The model has been further used to investigate the bases for the oceanic diurnal-precipitation cycle; the results thus obtained indicate that such an oceanic cycle occurs even in the absence of neighboring continents, and tends to have a morning maximum, although the observed phenomenon is generally stronger than the results indicate.

Surface Cyclogenesis over South America

Abstract: The frequency of surface cyclogenesis over South America (approximately the area enclosed by 15°–50°S and 30°–90°W) has been calculated using, 10 years (1979–1988) of data. The frequency of cyclogenesis is more in winter than in any other season. Highest frequency (139) is found in the month of May and the lowest frequency (71) is found in the month of December. In addition to seasonal, the frequency of cyclogenesis shows interannual variation. The occurrence of cyclogenesis is more during the years of negative Southern Oscillation index (El Nino years) and less during the years of positive Southern Oscillation index. The years of higher (lower) cyclogenesis are found to be associated with higher (lower) rainfall. This explains the negative correlation between the precipitation over southern Brazil and the Southern Oscillation index.

Deuterium excess in recent Antarctic snow

Abstract: Deuterium excess (d = δD - 8 * δ18O) values in surface snow are presented for central and east Antarctica. The samples are primarily from Soviet, French, and Australian traverses. The d values exhibit a large change going from coastal sites to high-altitude sites on the ice sheet. The d values are relatively constant at 3 to 6‰ from the coast to an altitude of 2500 m, and at higher elevations d increases steadily to values of 16 to 18‰ at Vostok and Plateau Station. The data is modeled as d versus δD using the kinetic Rayleigh model for isotopes in precipitation developed by Jouzel and Merlivat. The model accounts for kinetic fractionation during evaporation into undersaturated air over the ocean and during snow formation in <−10°C clouds where vapor is supersaturated with respect to snow. The overall pattern of d versus δD can be fit well with a supersaturation function which increases linearly with decreasing temperature and which predicts reasonable values of the supersaturation. Vapor originating from 20° to 60°S was tested with different supersaturation functions. The data could only be fit with moisture originating from 30° to 40°S, indicating that these latitudes are the main source of vapor for snow falling in Antarctica. The conclusion of a mid-latitude vapor source for polar snow agrees with the analysis of d and δ18O seasonal cycles in Greenland snow performed by Johnsen and coworkers. The model was also tested with moisture simultaneously originating from all latitudes from 30°S to the Antarctic coast. The addition of up to 20% of moisture evaporated from latitudes south of 50°, and 5% from latitudes south of 60°, is compatible with low d values occasionally observed in snow near the coast. The conclusion of a “local moisture” effect for coastal and near coastal (<2000 m elevation) snowfall supports a similar conclusion by Saigne and Legrand from their analysis of methanesulphonic acid in Antarctic snow. Finally, the effects of changes in the sea surface temperature and changes in oceanic humidity on the d values observed in Antartic snow are greatly modified during the precipitation process. Hence the interpretation of d values in ice cores should be done in the context of a precipitation model.

Effect of Catchment‐Scale Subsurface Mixing on Stream Isotopic Response

Abstract: A 3.8-ha watershed on the west coast of New Zealand was instrumented with suction lysimeters and automatic water samplers to determine the relationship between subsurface isotopic and chemical concentrations to those of rainfall and resulting streamflow. A t test showed that ±2‰ represented a significant difference between successive sample deuterium values. Eleven rainfall episodes were subdivided into two categories: (1) two events where stream isotopic composition did not deflect >2‰ from prestorm values, and (2) four events which demonstrated new water flushing. Detailed analysis of one 47-mm rainfall (9.8-mm runoff) event showed that old water dominated stream water exiting the watershed by 90% using a standard two-component hydrograph separation for deuterium (corroborated by Cl and electrical conductivity). Three-component hydrograph separation indicated that 12–16% was in the form of soil water, with <5% as on-channel precipitation and 80% groundwater. Analysis of over 1000 water samples revealed systematic trends in soil water and groundwater isotopic composition both in a downslope and downprofile direction. Between-storm suction lysimeter deuterium data showed a systematic dampened response to temporally variable rainfall deuterium concentrations. Multivariate cluster analysis revealed three distinct soil water/groundwater groupings, with respect to soil depth and geographic position within the watershed. Within-storm suction lysimeter sampling preserved similar groupings, indicating that the subsurface reservoir is poorly mixed on short time scales. Understanding subsurface mixing response to rainfall should greatly improve models of episodic stream response and partitioning of storm flow into waters of different age.

An 8‐year record of the seasonal variation of 2H and 18O in atmospheric water vapour and precipitation at Heidelberg, Germany

Abstract: Continuous time series of δD and δ 18 O in atmospheric water vapour and precipitation at Heidelberg are presented for the years 1981 to 1988. It is often not possible to derive the isotopic composition of the water vapour from the isotopic composition of precipitation for individual months. However, a close relationship does exist between the isotopic composition of the vapour and the precipitation on a timescale of a few years. The correlation of isotopic composition with temperature is much better for the vapour data than for the precipitation data. The Δδ/ΔT relationship of the seasonal variations is itself a function of temperature, being much lower during warmer periods than during cold periods. Especially during summer months, the admixture of water vapour originating from plant transpiration plays an important role in biasing the Δδ/ΔT relationship towards lower values. This effect complicates the calculation of palaeotemperatures using isotopic data. DOI: 10.1034/j.1600-0889.1991.t01-2-00003.x

Soil Moisture: Empirical Data and Model Results.

Abstract: A unique dataset of soil moisture in the upper 1-m soil layer at sites with natural plant cover in the Soviet Union is compared to simulations of soil moisture for the present climate by the Geophysical Fluid Dynamics Laboratory, Oregon State University, and United Kingdom Meteorological Office general circulation models. It is found that the present-day soil moisture regime is not well simulated by these models. Delworth and Manabe's hypothesis that the spectrum of time variations in soil moisture in the upper 1-m layer corresponds to a first-order Markov process with a decay time of the correlation function equal to the ratio of field capacity to potential evapotranspiration is empirically confirmed with this dataset. Analysis of measurement data over the 1972–1985 period reveals that the long-term trends of soil moisture north of 50°N are mainly due to increasing precipitation during this period of the same scale (1–3 cm/10 yr). The seasonal structure does not correspond to the “summer contine...

Simulation of precipitation by weather type analysis

Abstract: A method of precipitation simulation that incorporates climatological information has been developed. A Markovian-based model is used to generate temporal sequences of six daily weather types: high pressure; coastal return; maritime tropical return; frontal maritime tropical return; cold frontal overrunning; and warm frontal overrunning. Precipitation values are assigned to individual days by using observed statistical relations between weather types and precipitation characteristics. When this method was applied to an area in the Delaware River basin, the statistics describing average precipitation, extreme precipitation, and drought conditions for simulated precipitation closely matched those of the observed data. Potential applications of this weather type precipitation model include climatic change research and modeling of temperature and evapotranspiration.

An Explanation for the Existence of Supercooled Water at the Top of Cold Clouds

Abstract: Aircraft measurements in many cold cloud systems have found a narrow layer of supercooled water to exist at the cloud top, even at temperatures colder than −30°C. We show in this paper that the imbalance between the condensate supply rate and the bulk ice crystal mass growth rate at a wide range of temperatures and updraft speeds is sufficient to produce this liquid layer near cloud top because of the unique property that the ice crystals located there are small. Calculations are also presented to determine the minimum magnitude and maximum depth of a sustained updraft required to produce supercooled water near cloud top from an initially ice saturated cloud containing a population of ice crystals. Potential sources of the updraft circulations required to produce the liquid layer near cloud top are discussed. Finally, we consider the impact of the liquid layer on both cloud microstructure and precipitation processes.

Stratiform cloud formation in the marine boundary layer

Abstract: Observations of stratiform clouds in a region several hundred kilometers west of the southern California coast were made from the NCAR Electra research aircraft in the summer of 1987 during the First ISCCP (International Satellite Cloud Climatology Project) Regional Experiment (FIRE). Examples are shown of how heating or cooling of air by the sea and the evaporation of precipitation affect the stability of the temperature profile above the surface layer, which in turn affects the vertical moisture transports and the resulting cloud formation. We expect that sea-surface heating leads to the formation of stratus layers, while sea-surface cooling or cooling from evaporation of precipitation may produce fields of cumuli. The observations lead to a conceptual model of the life cycle of a stratus layer, starting as a thin, rather homogeneous layer, which grows and becomes patchy with time, produces precipitation, followed by formation of small cumuli below, and finally disintegrates, leaving a field of...

Microwave simulations of a tropical rainfall system with a three-dimensional cloud model

Abstract: A three-dinensional cloud model-microwave radiative transfer model combination is used to study the relations among the precipitation and other microphysical characteristics of a tropical oceanic squall line and the upwelling radiance at pertinent microwave frequencies. Complex brightness temperature-rain rate relations are evident at the full horizontal resolution (1.5 km) of the models, with spatial averaging producing smoother, shifter relations in most cases. Nonprecipitating cloud water is shown to be important in understanding the resulting distribution of brightness temperature. At the mature stage, convective portions of the cloud system are shown to produce different brightness temperature relations than the stratiform portion, primarily related to the distribution of cloud water. The evolution of the convective system from a small convective complex through its mature stage and the beginning of its dissipation also is shown to result in a variation of brightness temperature-rain relations, related to the distribution of cloud water and the evolution of ice in the precipitating system. The results of the study point to the need to take into account the evolution of nonprecipitating cloud water and precipitation-sized ice in the retrieval of rain from passive microwave space observations. This effect is evident for both the life cycle of individual convective elements and the life cycle of the convective system as a whole.

Precipitation Changes in Fall, Winter, and Spring Caused by St. Louis

Abstract: Analysis of precipitation events in the St. Louis aera, based on pre-event low-level wind flow, was pursued to ascertain the presence of urban effects on fall, winter, and spring precipitation. Data from a circular, dense, raingage network were used to define quadrant (NW, NE, SE, SW) average precipitation. Winds before each event (443 events in 1971–75) were used to define the urban plume and identify which quadrant was “downwind” of the city. Results for fall revealed a 17% increase in precipitation downwind of St. Louis and a 13% increase in events with their peak rainfall occurring downwind, both outcomes were statistically significant at the 1% level. The downwind enhancement was greatest when pre-event winds were from the SE, and when average precipitation in the quadrant with the maximum value was either light ( 17.9 mm). The fall results agree well with earlier findings for summer rainfall that revealed a 25% increase due to enhancement in isolated airmass showers...

Precipitation composition and its variability in the Southern Indian ocean : Amsterdam, Island, 1980-1987

Abstract: Event precipitation samples have been collected on Amsterdam Island (37° 47′ S, 77° 31′ E) from May 1980 through January 1987 and analyzed for SO4=, NO3−, Cl−, Na+, Mg++, K+, Ca++, H+, HCOOt, and CH3COOt. The objective of this paper is to assess the processes which influence variability in the chemical composition of precipitation at this remote marine site. Back trajectories and gas phase 222Rn measurements were used to identify source regions and their relative contributions to precipitation composition. The technique of cluster analysis was applied to trajectory data as a method for determining to what degree different atmospheric flow patterns influence variability in the observed composition. The dominant source regions for chemical deposition were found to be Madagascar and/or S.E. Africa and the ocean region north and east of Amsterdam Island. A strong seasonal signal in the precipitation composition is illustrated. Processes which influence variability in the chemical composition include the following: seasonality in the source strength of biogenic precursors for non-sea-salt (nss) SO4=, NH4+ and carboxylic acids; seasonality in biomass-burning continental sources for the concentration of NO3− and a portion of nss Cl−; and variations in source region driven by daily changes in meteorology, as well as seasonal and annual differences in transport and removal patterns. In addition, interannual differences in nss SO4= concentration appear to be related to fluctuations in large-scale circulation patterns as defined by the Southern Oscillation.

Hydrological balance of two Mediterranean forested catchments (Prades, northeast Spain)

Abstract: Precipitation and discharge have been measured for several years in two small forested catchments located in the Mediterranean area of Spain. Actual evapotranspiration has been calculated as the difference between annual precipitation and discharge. Results show that: (a) most of the precipitation is evaporated rather than lost by streamflow, even in the most humid years; (b) there is a high inter-annual variability both in discharge and evapotranspiration; and (c) annual evapotranspiration correlates significantly with annual precipitation, in contrast to the constancy of annual evaporation in catchments of wet, colder climates. Finally, a simple expression is proposed in order to calculate annual actual evaporation from the ratio of precipitation to potential evapotranspiration. This expression uses a derived exponent, k, which takes into account the characteristics of individual catchments.

Hydrologic characteristics and water balance of an Alpine Basin in the Sierra Nevada

Abstract: A water balance prepared for the Emerald Lake basin illustrates the absolute and relative magnitudes of the main water transfers in this alpine catchment in the Sierra Nevada over two water years. The water balance over both years, expressed as equivalent water depths averaged over the catchment area, was total precipitation (3670 mm)— total losses in the atmosphere (800 mm) = total streamflow (2830 mm) + residual (40 mm). Snow dominated the water balance during the study period, accounting for 95% of the precipitation. The spring snowmelt periods accounted for more than 85% of the annual streamflow and were followed by long recessions through summer, autumn, and winter. Estimated total evaporation from snow, water surfaces, soil, and vegetation at Emerald Lake was 22% of the estimated precipitation. Evaporation from snow was the principal water loss to the atmosphere, accounting for about 80% of the total evaporation. Actual evapotranspiration estimated over 15 non winter months was less than 4% of the precipitation during the two water years. Groundwater storage and release accounted for only a small portion of the total quantity of water in the annual water balance of this largely impermeable basin.

The Greenhouse Effect in Central North America: If Not Now, When?

Abstract: Climate models with enhanced greenhouse gas concentrations have projected temperature increases of 2 degrees to 4 degrees C, winter precipitation increases of up to 15 percent, and summer precipitation decreases of 5 to 10 percent in the central United States by the year 2030. An analysis of the climate record over the past 95 years for this region was undertaken in order to evaluate these projections. Results indicate that temperature has increased and precipitation decreased both during winter and summer, and that the ratio of winter-to-summer precipitation has decreased. The signs of some trends are consistent with the projections whereas others are not, but none of the changes is statistically significant except for maximum and minimum temperatures, which were not among the parameters predicted by the models. Statistical models indicate that the greenhouse winter and summer precipitation signal could have been masked by natural climate variability, whereas the increase in the ratio of winter-to-summer precipitation and the higher rates of temperature change probably should have already been detected. If the models are correct it will likely take at least another 40 years before statistically significant precipitation changes are detected and another decade or two to detect the projected changes of temperature.

Diagnosed Characteristics of Precipitation Systems over Taiwan during the May–June 1987 TAMEX

Abstract: Characteristics of Mei-Yu precipitating cloud systems over Taiwan during the May–June 1987 Taiwan Area Mesoscale Experiment (TAMEX) have been studied using sounding, surface precipitation, and radar data. Vertical motion has been computed over the island at 6-h intervals from 13 May to 15 June using a modification of the kinematic method that takes into account the mountainous lower boundary within a four-station sounding polygon. Two primary characteristics of the precipitation have been found. First, the major rainfall event were linked to the passage of midlatitude disturbances and typically consisted of both deep convective and stratiform components. Deep convection was primarily prefrontal or frontal, while the stratiform precipitation was postfrontal, presumably in association with overrunning and orographic lifting. Second, there was a pronounced diurnal variability in the rainfall. Vertical motion, heating (Q1), and moistening (Q2) profiles have been used to define the character of the pr...

The Effect of Heterogeneous Soil Moisture on a Summer Baroclinic Circulation in the Central United States

Abstract: Thermally induced circulations, similar to sea breezes, may be established in the presence of horizontal gradients in soil moisture, soil type, vegetation, or snow cover. The expense of extensive observational networks and the relatively small-scale circulations involved has made examining these circulations very difficult. Recent numerical studies have indicated that sharp gradients in soil or vegetation properties may induce mesoscale circulations in the absence of synoptic forcing. The current study employed a three-dimensional, hydrostatic mesoscale model to evaluate the effects of horizontally heterogeneous soil moisture and soil type on the passage of a summer cold front in the central United States. Grid-scale condensation, precipitation, latent heat release, and cumulus conviction are not accounted for in this model; moisture was affected only by advection, diffusion, and evaporation. Numerical simulations demonstrated that evaporation of soil moisture significantly affected the boundary ...

The Deposition, Composition, and Potential Sources of Major Ionic Solutes in Rain of the Central Amazon Basin

Abstract: Major solute concentrations were measured for 123 individual rainstorms greater than 1 mm that occurred over a continuous 18-month period (September 1983 through February 1985) in the central Amazon Basin The sum of concentrations was low (volume-weighted mean, 39 μeq/L), mean pH was 49, and the dominant source of acidity was organic acids Analyses of interactions among solute concentrations in storms of differing size, frequency, and season of occurrence permitted evaluation of how rainfall variation affects depositional rates of solutes The 20% of least frequent, large-volume storms accounted for about 75% of the water and almost 60% of the solutes deposited annually Depositional rates of total N and P, Na+, and SO42− did not differ substantially as rainfall varied, while Ca2+, Mg2+, Cl−, NO3− and PO43− did Wet deposition of N and P varied less than 20%, despite a threefold intraannual variation of rainfall Comparison between event and bulk precipitation samples indicated that dry deposition was minor except for P Ionic ratios relative to Na+, R mode and Q mode factor analyses of rainwater composition, and differences in deposition among seasons provide evidence for the seasonal-scale importance of biogenic emissions of aerosols and reduced S and N gases from the Amazon rain forest to the atmosphere

Occurrence of fog in Chile

Abstract: Abstract The topography in Chile is extremely complex and many types of fog are found; both factors complicate the presentation of the data. Despite this, measurements from standard meteorological stations suggest a latitudinal maximum in fog frequency between 35° and 40°S for coastal stations. This is supported by data from inland stations in Chile and the available observations from Argentina on the Atlantic coast of South America. Along the Chilean coast the average number of days with fog ranges from 3 to 59 per year. The variation in fog frequencies is related to persistent synoptic-scale circulation patterns and to ocean currents. Specialized fog observations wore made at three remote locations in northern Chile to determine fog frequencies on the coastal mountains. The sites were in a very add region (26°–28°S) near a large-scale fog-water collection project. Fog frequencies as high as 189 days per year with another 84 days of patchy fog were reported at an altitude of 860 m. These are 3–15 times h...

The evaporation of frontal and other stratiform precipitation

Abstract: SUMMARY The evaporation of precipitation of differing types is considered by use of one-dimensional models. It is shown that the evaporation of snow and crystalline ice precipitation takes place in shorter times and much shallower depths than for rain, while for graupel it falls between the two. The main factors responsible for the differences in behaviour are bulk density and terminal velocity of particles, which combine to produce evaporation depths for snow less than one tenth those for rain. Further, the evaporation depth predicted for snow is shown to be rather insensitive to detailed characteristics of the snow particles within the observed range. Some of the implications of this difference are explored by means of a model describing the interaction of evaporating precipitation with its environment when subjected to atmospheric descent. The model, originally due to Kamburova and Ludlam (1966), has been extended to study the evolution of a variable particle spectrum. It is shown that for rainfall rates of the order of I-l0mm h -’ the evaporation of snow is sufficient to maintain the atmosphere in a near-saturated condition despite descent rates of the order of 10-30cm s-’, typical of those observed on the mesoscale in stratiform environments like rainbands; rain exhibits no comparable behaviour. These results suggest that the evaporation of snow plays a major role in the dynamics of fronts and other mesoscale systems with stratiform cloud. This view is supported by comparison with dropsonde observations from the FRONTS 87 experiment, which show a clear indication of enhanced mesoscale descent in the region of maximum precipitation.

The effects of climate change on discharges and snow cover in Finland

Abstract: The effects of climate change obtained through model simulations on runoff and snow cover in Finland are presented in this study. The results are based on hydrological model simulations using the information from one climatic general circulation model (GISS) scenario with doubled atmospheric carbon dioxide as input. According to the GISS model scenario, the temperature increase in Finland will be 2–6®C, the precipitation increase 10–30 mm per month and the evaporation increase 5–30 mm per month. The effects of these climatic changes on runoff and snow cover have been evaluated in twelve different watersheds by hydrological watershed models. According to the results the mean discharge (MQ) increases by 20–50%, the mean minimum discharges (MNQ) increase considerably in winter due to a two to three months shorter snow cover period and the mean maximum discharges (MHQ) decrease due to diminished maximum snow water equivalents. In southern Finland persistent winter snow cover will vanish.

A Modeling Case Study of Interaction between Heavy Precipitation and a Low-Level Jet over Japan in the Baiu Season

Abstract: This paper presents results of simulations for a case of heavy precipitation that occurred on 23 July 1982 over western Japan. Special emphasis is placed on synoptic- and subsynoptic-scale processes that led to heavy precipitation and also its linkage with the low-level jet (LLJ). The model result recaptures the major observed features of this event reasonably well. The sequence of events revealed by the model starts with the formation of a localized surface warm front caused by the deformation field that is associated with an eastward traveling, nondeepening meso-αscale low. It is followed by the initiation of both concentrated convective precipitation at the surface front and stratiform grid-scale precipitation along the sloping frontal surface. The simulations with different model physics reveal significant roles that diabatic heating processes play in the linkage between heavy precipitation and the LLJ. While condensation heating produces a cyclonic circulation with failing pressure manifeste...