Summertime Precipitation Research Articles

Altitude Dependence of Trends of Summertime Precipitation during the Period 1979—2015 in Nagano Prefecture

Altitude Dependence of Trends of Summertime Precipitation during the Period 1979—2015 in Nagano Prefecture

Satellite-based soil moisture provides missing link between summertime precipitation and surface temperature biases in CMIP5 simulations over conterminous United States

Past studies have shown that climate simulations have substantial warm and dry biases during the summer in the conterminous United States (CONUS), particularly in the central Great Plains (CGP). These biases have critical implications for the interpretation of climate change projections, but the complex overlap of multiple land-atmosphere feedback processes make them difficult to explain (and therefore correct). Even though surface soil moisture (SM) is often cited as a key control variable in these processes, there are still knowledge gaps about its specific role. Here, we use recently developed remotely sensed SM products to analyse the link between spatial patterns of summertime SM, precipitation and air temperature biases over CONUS in 20 different CMIP5 simulations. We identify three main types of bias combinations: (i) a dry/warm bias over the CGP region, with a significant inter-model correlation between SM and air temperature biases (R = −0.65), (ii) a wet/cold bias in NW CONUS, and (iii) a dry/cold bias in SW CONUS. Combined with irrigation patterns, these results suggest that land-atmosphere feedbacks over the CGP are not only local but have a regional dimension, and demonstrate the added-value of large-scale SM observations for resolving the full feed-back loop between precipitation and temperature.

Urban Rainfall Modification: Observational Climatology Over Berlin, Germany

AbstractThis study investigates the direct influence of urban areas on storm events (heavy rainfall above 17 mm/hr). An 11‐year climatology of summertime precipitation was performed to capture and describe storm events for Berlin, Germany. An hourly radar composite product from the German Weather Service with a 1‐km grid resolution was used for the analysis. Berlin was chosen due to the relatively modest influences of topography and distinct urban‐rural landscape heterogeneity potentially affecting storms. The analysis identified 96 storm events for the period from 2006 to 2016. Individual storm characteristics were evaluated before the city (upwind), over the city, and behind the city (downwind). Both visual and statistical estimations quantified storm modifications caused by the urban area. Around 60% of the events showed typical patterns of storm alteration by the city. In conformance to earlier studies, we found evidence of urban rainfall intensification about 20 to 50 km downwind of the urban center. Most storms were suppressed, deflected, or split by the city, whereas intensification over the city typically occurred at night or when storms formed over the city. In the present study, results indicate an urban influence on storms in and around Berlin. But, unlike other studies, downwind intensification of storm rainfall was not a typical feature. This study on urban rainfall modification marks one of the first observations‐based climatological assessments for the European region.

The role of anthropogenic aerosols in future precipitation extremes over the Asian Monsoon Region

The role of anthropogenic aerosols in future projections (up to 2100) of summertime precipitation and precipitation extremes over the Asian monsoon region is investigated, by comparing two sets of the Community Earth System Model (CESM1) large ensemble simulations under the Representative Concentration Pathway 8.5 scenario (RCP8.5) and the corresponding scenario with aerosol fixed at 2005 levels (RCP8.5_FixA). The model is verified to be performing well in capturing present-day (1986–2005) climate and precipitation extremes. Our results suggest that the Asian monsoon region would become progressively warmer and wetter in the future under RCP8.5, while precipitation extremes will be significantly aggravated due to anthropogenic aerosol mitigation, particularly over East Asia. Specifically, aerosol reductions are found to shift the distribution of precipitation mean and extremes to larger values. For example, aerosol reductions would result in an increased likelihood of extreme precipitation (e.g. the maximum consecutive 5-day precipitation amount) and related disasters. Sensitivities of changes in precipitation mean and extremes to local warming from aerosol reductions are much larger than that from greenhouse gas increases. This is particularly important over East Asia in accordance with larger magnitudes of aerosol reductions compared to South Asia. Finally, by investigating the response of the climate system to aerosol changes, our findings demonstrate that aerosol induced precipitation changes would be dominated by aerosol–radiation–cloud forcing over northern East Asia and aerosol forcing induced large-scale circulation anomalies over southern East and South Asia.

Climate change effects on summertime precipitation organization in the Southeast United States

As the earth warms, it is unclear how the organization of precipitation will change, or how these changes will impact regional rainfall and the hydrological cycle. This study combines Weather Research and Forecasting (WRF) model simulations and the pseudo global warming downscaling approach with a precipitation feature identification algorithm to help improve our understanding of the effect of warming on precipitation organization. The WRF model was used to simulate precipitation during a six-day summer period in the southeastern United States under present and future warmer climate conditions. The domain averaged precipitation increased by 45% in the future climate simulation compared to current climate. Modeled precipitation features were classified into either mesoscale precipitation features (MPF) larger than 100 km in length or smaller isolated precipitation features (IPF). In terms of organization, future IPF precipitation fraction decreased while MPF precipitation fraction and feature sizes increased, especially over the ocean, indicating a general increase in mesoscale organization in the future warmer climate. Despite higher thermodynamic instability, future climate IPF precipitation was unchanged over land, possibly responding to stronger subsidence under a strengthened western ridge of the North Atlantic Subtropical High. Yet over the ocean IPF precipitation increased and the amplitude of the IPF diurnal cycle doubled. The most notable precipitation intensity increase, as measured by feature height and rainrate distributions, occurred in oceanic MPFs. These increases in oceanic IPF and MPF precipitation may highlight the role of surface water vapor fluxes in realizing increased precipitation in a warmer climate. This study demonstrates that the application of a simple precipitation feature identification algorithm to WRF simulations can give valuable insight into the effect of climate change upon precipitation organization and intensity. Nevertheless longer simulations are still needed to obtain a robust statistics of the changes of precipitation organization under a warming climate.

Tree-Ring Carbon Isotope Records from the Western Oregon Cascade Mountains Primarily Record Summer Maximum Temperatures

Abstract Here we examine climatic influences on inter-annual variation in latewood tree growth (i.e. ring-width indices, RWILW) and stable-carbon isotope discrimination (Δ13CLW) from 1950 to 2013 at two SNOTEL snowpack monitoring sites in the Oregon Cascade Mountains. Douglas-fir and mountain hemlock trees were sampled at the lower and upper elevation sites where annual peak snow water equivalent (SWE) averaged 467 and 1128 mm, respectively. RWILW chronologies were poorly correlated among sites/species (r = 0.23, P = 0.063) and neither exhibited strong correlations with monthly or seasonal climate variables. By contrast, Δ13CLW chronologies were significantly correlated (r = 0.69, P < 0.001) and exhibited stronger climate responses. Multiple regression analyses identified summertime maximum temperature (Tmax) and/or vapor pressure deficit (VPD) as the primary drivers of Δ13CLW. Secondary influences included summertime precipitation, specific humidity, cloud cover, and SWE from the previous fall and winter...

Efficacy of tendency and linear inverse models to predict southern Peru's rainy season precipitation

ABSTRACTSouthern Peru receives over 60% of its annual climatological precipitation during the short period of January–March. This rainy season precipitation exhibits strong inter‐annual and decadal variability, including severe drought events that incur devastating societal impacts and cause agricultural communities and mining facilities to compete for limited water resources. Improving existing seasonal prediction models of summertime precipitation could aid in water resource planning and allocation across this water‐limited region. While various underlying mechanisms modulating inter‐annual variability have been proposed by past studies, operational forecasts continue to be largely based on rudimentary El Niño‐Southern Oscillation (ENSO)‐based indices, such as Niño3.4, justifying further exploration of predictive skill. To bridge the gap between understanding precipitation mechanisms and operational forecasts, we perform systematic studies on the predictability and prediction skill of southern Peru's rainy season precipitation by constructing statistical forecast models using best available weather station and reanalysis data sets. We construct a simple regression model, based on the principal component (PC) tendency of tropical Pacific sea surface temperatures (SST), and a more advanced linear inverse model (LIM), based on the empirical orthogonal functions of tropical Pacific SST and large‐scale atmospheric variables from reanalysis. Our results indicate that both the PC tendency and LIM models consistently outperform the ENSO‐only based regression models in predicting precipitation at both the regional scale and for individual station, with improvements for individual stations ranging from 10 to over 200%. These encouraging results are likely to foster further development of operational precipitation forecasts for southern Peru.

Role and Impact of the Urban Environment in a Numerical Forecast of an Intense Summertime Precipitation Event over Tokyo

Role and Impact of the Urban Environment in a Numerical Forecast of an Intense Summertime Precipitation Event over Tokyo

Influence of the North Atlantic Subtropical High on wet and dry sea-breeze events in North Carolina, United States

The sea-breeze (SB) is an important source of summertime precipitation in North Carolina (NC, southeast United States). However, not all SB events produce precipitation. A climatology of wet and dry SB events in NC is used to investigate the conditions that are conducive to precipitation associated with the sea breeze. Radar imagery was used to detect 88 SB events that occurred along the NC coast between May-September of 2009-2012. The majority (85%) of SB events occurred during offshore flow (53%) or during flow that was parallel to the coast (22%). SB events were separated into dry (53%) and wet (47%) events and differences in the dynamic and thermodynamic parameters of the environment in which they formed were analyzed. Significant differences in dynamic and thermodynamic conditions were found. SB dry events occurred under stronger winds (6.00 ± 2.36 ms-1) than SB wet events (4.02 ± 2.16 ms-1). Moreover, during SB wet events larger values of convective available potential energy and lower values of convective inhibition were present, conditions that favor precipitation. Overall, the SB wet events accounted for 20-30% of the May-September precipitation along the NC coastal region. The position of the North Atlantic Subtropical High (NASH) controls both moisture availability and winds along the NC coast, thus providing a synoptic-scale control mechanism for SB precipitation. In particular, it was shown that when the NASH western ridge is located along the southeast coast of the United States, it causes a moist southwesterly flow along the NC coast that may favor the occurrence of SB wet events.

Influence of the West Pacific subtropical high on surface ozone daily variability in summertime over eastern China

The West Pacific subtropical high (WPSH), as one of the most important components of the East Asian summer monsoon (EASM), is the key synoptic-scale circulation pattern influencing summertime precipitation and atmospheric conditions in China. Here we investigate the impacts of the WPSH on surface ozone daily variability over eastern China, using observations from recently established network of ozone monitors and meteorology reanalysis data during summer (June, July, August; JJA) 2014–2016 with a focus on 2014. An empirical orthogonal function (EOF) analysis of daily ozone variations reveals that the dominating eigenvector (EOF1), which contributes a quarter (25.2%) to the total variances, is a marked north-south contrast. This pattern is temporally well correlated (r = −0.66, p < 0.01) with daily anomalies of a normalized WPSH intensity index (WPSH-I). Spatially, the WPSH-I and ozone correlation is positive in North China (NC) but negative in South China (SC), which well correlates with the ozone EOF1 pattern showing the same north-south contrast (r = −0.86, p < 0.01). These associations suggest the dominant component of surface ozone daily variability in eastern China is linked with the variability of the WPSH intensity in that a stronger WPSH leads to a decrease of surface ozone over SC but an increase over NC and vice versa. This is because a stronger WPSH enhances southwesterly transport of moisture into SC, creating such conditions not conducive for ozone formation as higher RH, more cloudiness and precipitation, less UV radiation, and lower temperature. Meanwhile, as most of the rainfall due to the enhanced southwesterly transport of moisture occurs in SC, water vapor is largely depleted in the air masses transported towards NC, creating dry and sunny conditions over NC under a strong WPSH, thereby promoting ozone formation.

Understanding the influence of orography on the precipitation diurnal cycle and the associated atmospheric processes in the central Andes

In the tropical Andes, the identification of the present synoptic mechanisms associated with the diurnal cycle of precipitation and its interaction with orography is a key step to understand how the atmospheric circulation influences the patterns of precipitation variability on longer time-scales. In particular we aim to better understand the combination of the local and regional mechanisms controlling the diurnal cycle of summertime (DJF) precipitation in the Northern Central Andes (NCA) region of Southern Peru. A climatology of the diurnal cycle is obtained from 15 wet seasons (2000–2014) of 3-hourly TRMM-3B42 data (0.25° × 0.25°) and swath data from the TRMM-2A25 precipitation radar product (5 km × 5 km). The main findings are: (1) in the NCA region, the diurnal cycle shows a maximum precipitation occurring during the day (night) in the western (eastern) side of the Andes highlands, (2) in the valleys of the Cuzco region and in the Amazon slope of the Andes the maximum (minimum) precipitation occurs during the night (day). The WRF (Weather Research and Forecasting) regional atmospheric model is used to simulate the mean diurnal cycle in the NCA region for the same period at 27 km and 9 km horizontal grid spacing and 3-hourly output, and at 3 km only for the month of January 2010 in the Cuzco valleys. Sensitivity experiments were also performed to investigate the effect of the topography on the observed rainfall patterns. The model reproduces the main diurnal precipitation features. The main atmospheric processes identified are: (1) the presence of a regional-scale cyclonic circulation strengthening during the afternoon, (2) diurnal thermally driven circulations at local scale, including upslope (downslope) wind and moisture transport during the day (night), (3) channelization of the upslope moisture transport from the Amazon along the Apurimac valleys toward the western part of the cordillera.

Austral summer Southern Africa precipitation extremes forced by the El Niño-Southern oscillation and the subtropical Indian Ocean dipole

Southern Africa, defined here as the African continent south of 15°S latitude, is prone to seasonal precipitation extremes during December–March that have profound effects on large populations of people. The intensity of summertime precipitation extremes can be remarkable, with wet seasons experiencing up to a doubling of the seasonal average precipitation. Recognizing the importance of understanding the causes of Southern Africa precipitation extremes for the purpose of improved early warning, an 80-member ensemble of atmospheric model simulations forced by observed time-varying boundary conditions during 1979–2016 is used to examine the mechanisms by which December–March precipitation extremes are delivered to Southern Africa and whether the El Nino-Southern Oscillation (ENSO) and the Subtropical Indian Ocean Dipole (SIOD) modify the probabilities of extreme seasonal precipitation occurrences. The model simulations reveal that the synchronous ENSO and SIOD phasing conditions the probability of December–March extreme precipitation occurrences. The probability of extreme wet seasons is greatly increased by La Nina, especially so when combined with a positive SIOD, and greatly decreased by El Nino regardless of SIOD phasing. By contrast, the probability of extreme dry seasons is increased by El Nino and is decreased by La Nina. The mechanisms by which extreme precipitation are delivered are the same regardless of ENSO and SIOD phase. Extreme wet seasons are a result of an anomalous lower tropospheric cyclone over Southern Africa that increases convergence and moisture fluxes into the region while extreme dry seasons are a result of an anomalous lower tropospheric anticyclone that decreases convergence and moisture fluxes into the region.

Statistically extrapolated nowcasting of summertime precipitation over the Eastern Alps

This paper presents a new multiple linear regression (MLR) approach to updating the hourly, extrapolated precipitation forecasts generated by the INCA (Integrated Nowcasting through Comprehensive Analysis) system for the Eastern Alps. The generalized form of the model approximates the updated precipitation forecast as a linear response to combinations of predictors selected through a backward elimination algorithm from a pool of predictors. The predictors comprise the raw output of the extrapolated precipitation forecast, the latest radar observations, the convective analysis, and the precipitation analysis. For every MLR model, bias and distribution correction procedures are designed to further correct the systematic regression errors. Applications of the MLR models to a verification dataset containing two months of qualified samples, and to one-month gridded data, are performed and evaluated. Generally, MLR yields slight, but definite, improvements in the intensity accuracy of forecasts during the late evening to morning period, and significantly improves the forecasts for large thresholds. The structure–amplitude–location scores, used to evaluate the performance of the MLR approach, based on its simulation of morphological features, indicate that MLR typically reduces the overestimation of amplitudes and generates similar horizontal structures in precipitation patterns and slightly degraded location forecasts, when compared with the extrapolated nowcasting.

Simultaneous modulations of precipitation and temperature extremes in Southern parts of China by the boreal summer intraseasonal oscillation

The boreal summer intraseasonal oscillation (BSISO), including a 30–60 day component (BSISO1) and a quasi-biweekly component (BSISO2), is the most prominent form of subtropical intraseasonal variability. Influences of BSISOs on summertime precipitation and temperature extremes in China are examined. Results indicate that BSISOs can simultaneously facilitate precipitation extremes in central-eastern China and extreme high temperatures in South China-Southeast China. During phase 2–4 of active BSISO1, accompanying precipitation extremes in central-eastern China, there is a fourfold-fivefold increase in probability of extreme high temperatures in Southeast China. About 50% of such simultaneous extremes fall into phase 2–3. BSISO2’s influences are pronounced from phase 6 to the next phase 2, with about 58% simultaneous extremes clustered within phase 7 to the next phase 1. It is the BSISO-induced vertical cell, with ascending motion in the Yangtze-Huai River Valley and descending motion in the south, that contributes to simultaneous extremes. Enhanced low-level southwesterlies convey moist and warm air towards southern parts of China. Strengthened ascending branch loaded by anomalously abundant moisture produces precipitation extremes in the north. Concurrently, combined effects of warm advection and descent-triggered adiabatic heating anchors extreme high temperatures well located in South China. The northeastward propagation of the BSISO1 confines influenced regions to eastern-southeastern parts of China, with gradually narrowing spatial extents. The BSISO2-induced simultaneous extremes sweep much broader areas, from southeast coasts to the central inlands. Above analyses on BSISOs-simultaneous extremes relationship lay a crucial scientific basis for predicting these high-impact events on sub-seasonal to seasonal scales.

Changes in Spatiotemporal Precipitation Patterns in Changing Climate Conditions

AbstractClimate models robustly imply that some significant change in precipitation patterns will occur. Models consistently project that the intensity of individual precipitation events increases by approximately 6%–7% K−1, following the increase in atmospheric water content, but that total precipitation increases by a lesser amount (1%–2% K−1 in the global average in transient runs). Some other aspect of precipitation events must then change to compensate for this difference. The authors develop a new methodology for identifying individual rainstorms and studying their physical characteristics—including starting location, intensity, spatial extent, duration, and trajectory—that allows identifying that compensating mechanism. This technique is applied to precipitation over the contiguous United States from both radar-based data products and high-resolution model runs simulating 80 years of business-as-usual warming. In the model study the dominant compensating mechanism is a reduction of storm size. In summer, rainstorms become more intense but smaller; in winter, rainstorm shrinkage still dominates, but storms also become less numerous and shorter duration. These results imply that flood impacts from climate change will be less severe than would be expected from changes in precipitation intensity alone. However, these projected changes are smaller than model–observation biases, implying that the best means of incorporating them into impact assessments is via “data-driven simulations” that apply model-projected changes to observational data. The authors therefore develop a simulation algorithm that statistically describes model changes in precipitation characteristics and adjusts data accordingly, and they show that, especially for summertime precipitation, it outperforms simulation approaches that do not include spatial information.

The impact of atmospheric blocking on spatial distributions of summertime precipitation over Eurasia

The correlation of precipitation anomalies over Eurasia with atmospheric blocking events was examined with ERA Interim reanalysis data. We found that, regardless of the frequency of the atmospheric blocking events, they significantly affect the distribution of rainfall over all Eurasian regions in summer, due to both the change in the westerly transport and the dominant dipole blocking structure. It is important that, depending on the blocking positions in Asia, there are heavy rainfalls in an arid zone which includes Kazakhstan, Mongolia, Northern China, and the Trans-Baikal Territory.

Is the global atmospheric model MRI-AGCM3.2 better than the CMIP5 atmospheric models in simulating precipitation over East Asia?

The reproducibility of precipitation over East Asia (110–150°E, 20–50°N) by the Meteorological Research Institute-Atmospheric General Circulation Model version 3.2 (MRI-AGCM3.2) was investigated and compared with those by global atmospheric models participated in the fifth phase of the Coupled Model Intercomparison Project (CMIP5). The 20, 60 and 180-km grid size version of this model were used to evaluate the dependence of model performance on horizontal resolution. The dependence of cumulus convection scheme on model performance was also investigated. All the MRI-AGCM3.2 models and the CMIP5 models were forced with observed historical sea surface temperatures for the period 1979–2003 (25 years). The reproducibility of the MRI-AGCM3.2 models is higher or comparable to that of the CMIP5 models for seasonal average precipitation, the seasonal March of rainy zone and extreme precipitation events. Especially in summer, the advantage of the MRI-AGCM3.2 models over the CMIP5 models is striking in terms of various skill measures. This is partly due to the higher horizontal resolution of the MRI-AGCM3.2 models, but the performance of models is also sensitive to and depends on cumulus convection scheme. The better simulation of summer precipitation over East Asia by the MRI-AGCM3.2 models can be partly attributed to the better simulation of precipitation, the West Pacific Subtropical High and the local Hadley circulation in the tropics. This study highlights that higher reproducibility of summertime precipitation over East Asia requires proper simulation not only for tropical circulation but also for the strong dynamical linkage between precipitation over East Asia and tropical circulation.

Continental-scale convection-permitting modeling of the current and future climate of North America

Orographic precipitation and snowpack provide a vital water resource for the western U.S., while convective precipitation accounts for a significant part of annual precipitation in the eastern U.S. As a result, water managers are keenly interested in their fate under climate change. However, previous studies of water cycle changes in the U.S. have been conducted with climate models of relatively coarse resolution, leading to potential misrepresentation of key physical processes. This paper presents results from a high-resolution climate change simulation that permits convection and resolves mesoscale orography at 4-km grid spacing over much of North America using the Weather Research and Forecasting (WRF) model. Two 13-year simulations were performed, consisting of a retrospective simulation (October 2000–September 2013) with initial and boundary conditions from ERA-interim and a future climate sensitivity simulation with modified reanalysis-derived initial and boundary conditions through adding the CMIP5 ensemble-mean high-end emission scenario climate change. The retrospective simulation is evaluated by validating against Snowpack Telemetry (SNOTEL) and an ensemble of gridded observational datasets. It shows overall good performance capturing the annual/seasonal/sub-seasonal precipitation and surface temperature climatology except for a summer dry and warm bias in the central U.S. In particular, the WRF seasonal precipitation agrees with SNOTEL observations within a few percent over the mountain ranges, providing confidence in the model’s estimation of western U.S. seasonal snowfall and snowpack. The future climate simulation forced with warmer and moister perturbed boundary conditions enhances annual and winter-spring-fall seasonal precipitation over most of the contiguous United States (CONUS), but suppresses summertime precipitation in the central U.S. The WRF-downscaled climate change simulations provide a high-resolution dataset (i.e., High-Resolution CONUS downscaling, HRCONUS) to the community for studying one possible scenario of regional climate changes and impacts.

The boreal winter Madden‐Julian Oscillation's influence on summertime precipitation in the greater Caribbean

AbstractPrecipitation totals in the greater Caribbean are known to be affected by interannual variability. In particular, dry conditions in the spring‐summer have been physically linked to the positive phase of North Atlantic Oscillation (NAO) in the literature. In this study, it was found through regression analysis that an active Madden‐Julian Oscillation (MJO) in winter geographically focused over the Maritime Continent contributes to a positive NAO in March via the generation of Rossby waves in the Northern Hemisphere. Specifically, a negative Pacific‐North American pattern develops in the winter and transitions to an Atlantic pattern in spring. The positive NAO is a transient feature of this evolving wave train, but a center of significant positive 200 hPa geopotential heights is entrenched over the southeast U.S. throughout the February to May time period and is manifested as high pressure at the surface. The southern flank of this system increases the speeds of the trade winds and leads to a cooling of the Caribbean sea surface temperatures and, thus, convection suppression and reduced precipitation. Thus, this study advances our understanding of the climate of the greater Caribbean by using climate teleconnections to relate the MJO to rainfall in the region.

Tropical and Extratropical Controls of Gulf of California Surges and Summertime Precipitation over the Southwestern United States

AbstractIn this study ERA-Interim data are used to study the influence of Gulf of California (GoC) moisture surges on the North American monsoon (NAM) precipitation over Arizona and western New Mexico (AZWNM), as well as the connection with larger-scale tropical and extratropical variability. To identify GoC surges, an improved index based on principal component analyses of the near-surface GoC winds is introduced. It is found that GoC surges explain up to 70% of the summertime rainfall over AZWNM. The number of surges that lead to enhanced rainfall in this region varies from 4 to 18 per year and is positively correlated with annual summertime precipitation. Regression analyses are performed to explore the relationship between GoC surges, AZWNM precipitation, and tropical and extratropical atmospheric variability at the synoptic (2–8 days), quasi-biweekly (10–20 days), and subseasonal (25–90 days) time scales. It is found that tropical and extratropical waves, responsible for intrusions of moist tropical air into midlatitudes, interact on all three time scales, with direct impacts on the development of GoC surges and positive precipitation anomalies over AZWNM. Strong precipitation events in this region are, however, found to be associated with time scales longer than synoptic, with the quasi-biweekly and subseasonal modes playing a dominant role in the occurrence of these more extreme events.