Evaluation of Diverse-based Precipitation Data Over the Amazon Region

The skill of the diverse-based precipitation products is investigated in comparison with HYBAM rain-gauge observations. The performance of three remote sensing-based datasets (the Climate Hazards Group InfraRed Precipitation with Station, CHIRPS, the Multi-Source Weighted-Ensemble Precipitation, MSWEP, and the Tropical Rainfall Measuring Mission, TRMM) is evaluated considering different timescales for the Amazon Basin, an area with widely heterogeneous precipitation. The analysis considered seasonal, intraseasonal and diurnal timescales through the computation of the cluster analysis, the seasonality index, the Kling-Gupta Efficiency metric, spectral analysis and composing technique. CHIRPS has the lowest performance to represent the rainfall in the northwest portion of the basin, where it underestimated the mean precipitation compared to the other bases. In this region, the other remote sensing-based (TRMM and MSWEP databases) compared to HYBAM also showed considerable variability and misrepresentation of the intraseasonal rainfall. In general, all databases perform better in the north and eastern portions of the basin compared to HYBAM. The comparison of the diurnal rainfall cycle between remote sensing-based data and the field campaigns of TRMM-LBA and GoAmazon, and the Huayao station in the Andes was also evaluated. At the diurnal timescale, MSWEP predates the time of the rainfall peak, but represents the magnitude of the precipitation well compared with TRMM. This study is necessary to warn about the importance of a more complete and objective assessment of the data before considering it for applications in different precipitation studies, mainly in regions with high rainfall heterogeneity like the Amazon Basin.

RESPON CURAH HUJAN DIURNAL TERHADAP MADDEN-JULIAN OSCILLATION AKTIF DI BENUA MARITIM BERBASIS GSMAP GAUGE-CALIBRATED V7

Intisari Keberadaan pergeseran puncak curah hujan diurnal (DR) terhadap Madden-Julian Oscillation (MJO) aktif di Maritime Continent (MC) masih diperdebatkan sehingga studi ini bertujuan untuk menginvestigasi perubahan tersebut. Selain itu, intensitas rata-rata dan amplitudo DR juga dikaji dalam penelitian ini berbasis GSMaP Gauge-Calibrated V7. Komposit anomali intensitas rata-rata (Ra), amplitudo (Rax) DR MJO aktif dan perbandingan fase puncak DR MJO aktif terhadap klimatologinya (Pax-Pm) pada periode Desember-Januari-Februari (DJF), Maret-April-Mei (MAM), Juni-Juli-Agustus (JJA) dan September-Oktober-November (SON) digunakan dalam tulisan ini dengan uji-z 80%. MJO aktif berbasis rekonstruksi outgoing longwave radiation (OLR) dari kedua indeks realtime multivariate MJO (RMM). Hasil memperlihatkan bahwa MJO aktif memodulasi peningkatan intensitas rata-rata dan amplitudo DR di lautan dan mempengaruhi pergeseran puncak DR menjadi lebih cepat 1 jam dari klimatologi musimannya. Abstract The occurrence of peak phase shift of diurnal rainfall (DR) to active Madden-Jullian Oscillation (MJO) has been debatable, so this study is aimed to investigate the change. Moreover, the mean and amplitude intensity of DR were also analyzed in this study based on GSMaP Gauge-Calibrated V7. The composite of the mean (Ra) and amplitude (Rax) intensity anomaly of DR, and the comparison of DR peak phase during the active MJO to its climatology (Pax-Pm) in the period December-January-February (DJF), March-April-May (MAM), June-July-August (JJA), and September-October-November (SON) were used in the study with the z-test of 80%. The active MJO was based on reconstructed outgoing longwave radiation (OLR) of two real-time multivariate MJO (RMM) indexes. The results showed that active MJO modulated the increased mean and amplitude intensity of DR over the ocean and influenced the DR peak phase shift to be faster than its seasonal climatology by one hour.

Evaluating Diurnal Rainfall Signal Performance from CMIP5 to CMIP6

This study provides a comprehensive overview of diurnal rainfall signal performance within the current collection of models in Phase 6 of the Coupled Model Inter-comparison Project (CMIP6). The results serve as a reference for understanding model physics performance to represent precipitating processes and atmosphere–land–ocean interactions in response to the diurnal solar radiation cycle. Performance metrics are based on the phase, amplitude, and two empirical orthogonal function (EOF) modes of the climatological diurnal rainfall cycle derived from a Tropical Rainfall Measurement Mission observational dataset. We found that the ensemble model biases of diurnal phase and amplitude over lands improved from CMIP5 to CMIP6; however, those over oceans are still highly uncertain among CMIP6 models. Evaluation with observed EOF modes shows that the CMIP6 models are bifurcated based on the second EOF (EOF2), which represents diurnal rainfall contrast of coastal regimes where large biases of phase and amplitude reside. While the model ensemble suggests models are benefited from higher resolution in simulating phase and amplitude biases, the most distinct difference between the bifurcations is that one group successfully captures prevailing nighttime rainfall over tropical islands and coasts, especially over the Maritime Continent. Convective rainfall diagnosed by cumulus parameterization is found to be responsible for such biases. Our results suggest that CMIP6 models have generally been improved in their representation of diurnal rainfall cycles; however, for coastal diurnal regimes, more study is needed to improve the model parameterization of precipitation processes interacting with islands and coastal regions as current model resolution is still too coarse to resolve them.

Adaptation to Extreme Hydrological Events by Javanese Society through Local Knowledge

Understanding the effects of local knowledge on actions and decisions taken during a crisis is important; empirical studies and scientific data can be instructive to this end. This study integrated local knowledge (Pranata Mangsa) in Jawa, Indonesia, with scientific data on diurnal rainfall, extreme precipitation events, using the Local and Indigenous Knowledge System (LINKS). The results showed that Pranata Mangsa has informed aspects of agriculture including crop calendars, crop patterns, and farming activities, for over 1000 years in Jawa. Pranata Mangsa also enhances community resilience by mitigating the effects of extreme droughts; this finding was validated using scientific data.

Resolution-Dependent Perspectives on Caribbean Hydro-Climate Change

Near-surface winds around the mountainous Caribbean islands contribute to orographic lifting and thermal diurnal rainfall that requires mesoscale analysis. Here, a new perspective is presented via high-resolution satellite and reanalysis products. Singular value decomposition is applied to 5 km cold-cloud duration satellite data to understand the leading mode of seasonal hydro-climate variability and its regional controls. The spatial loadings reflect wet islands in a dry marine climate, while temporal amplitude is modulated by the large-scale zonal circulation. When summer-time trade winds weaken, daytime confluence around Caribbean islands enlarges, gathering and lifting more moisture. In addition to the static geographic forcing, transient easterly waves impart the majority of marine rainfall between June and September. Higher resolution products capture the thermal orographic effect and reveal upward trends in island rainfall and soil moisture over the satellite era, while lower resolution products miss this effect. The climate of mountainous Caribbean islands is trending toward increased runoff and soil moisture.

What Drives Daily Precipitation Over Central Amazon? Differences Observed Between Wet and Dry Seasons

This study suggests a new approach on how diurnal precipitation is modulated by the nighttime events developed over Central Amazon using data from the Observations and Modelling of the Green Ocean Amazon (GoAmazon 2014/5) field campaign in the Central Amazon as well as radar and satellite data. Local observations of cloud occurrences, soil temperature, surface fluxes, and planetary boundary layer characteristics are coupled with satellite data to identify physical mechanisms that control the diurnal rainfall in Amazonas during the wet and dry season. This is accomplished by evaluating the atmospheric properties during the nocturnal periods from the days prior to rainfall and non-raining events. Comparisons between non-rainy and rainy transitions are presented for the wet (January to April) and dry (June to September) seasons. The results suggest that wet season diurnal precipitation is modulated mainly by night-time cloud coverage and local effects such as turbulence, while dry season rain events are mainly controlled by large-meso scale circulation.

Characteristics of Diurnal Rainfall over Peatland Area of South Sumatra, Indonesia

The peak time of rainfall occurrence over an area has certain characteristics in which the difference in time and intensity of rainfall varies depending on its location and distance from the sea. This variation can be determined based on the phase and amplitude obtained using harmonic analysis. In this study, combined data from in-situ observation, satellite remote sensing and reanalysis were used to analyze spatial and temporal variations of peak rainfall events over peatland area of the South Sumatra Province. The results show that most of the South Sumatra Province has a diurnal peak of rainfall during afternoon ranging from 16.00 to 19.00 Western Indonesian Time. In addition, the results also indicate that the analysis on the in situ data revealed seasonal variation both in amplitude and time of maximum diurnal rainfall, while the reanalysis data only indicated a weak seasonal variation on the amplitude of the diurnal rainfall. Furthermore, spatial analysis shows that the time of maximum diurnal rainfall has spatial variation. Over the ocean, the time of maximum diurnal rainfall occurs during night time/early morning. Over the lowland or coastal area, the time of maximum diurnal rainfall occurs during afternoon, while over the high altitude (mountain) it occurs during late night.

Gravity Waves and Other Mechanisms Modulating the Diurnal Precipitation over One of the Rainiest Spots on Earth: Observations and Simulations in 2016

ABSTRACT The diurnal cycle of precipitation and thermodynamic profiles over western Colombia are examined in new GPM satellite rainfall products, first-ever research balloon launches during 2016 over both sea and land, and numerical simulations with the Weather Research and Forecasting (WRF) Model. This paper evaluates the Mapes et al. mechanism for midnight–early morning coastal convection that propagates offshore: reduction of inhibition in the crests of lower-tropospheric internal waves. Shipborne balloon launches confirm the evening development of such inhibition by a warm overhang in saturation moist static energy (SMSE) near 700–800 hPa. This feature relaxes overnight, consistent with the disinhibition hypothesis for early morning rains. Over the coastal plain, soundings also show late afternoon increases in near-surface MSE large enough to predominate over the overhang’s inhibition effect, driving a second peak in the rainfall diurnal cycle. Parameterized convection simulations fail to simulate the observed coastal rainfall. Still, during a November 2016 wet spell, a cloud-permitting one-way nested 4 km simulation performs better, simulating morning coastal rainfall. In that simulation, however, early morning cooling in the 700–800 hPa layer appears mainly as a standing signal resembling the local radiative effect rather than as a propagating wave. We consider the additional hypothesis that the offshore propagation of that morning convection could involve advection or wind shear effects on organized convective systems. Strong easterlies at mountaintop level were indeed simulated, but that is one of the model’s strongest biases, so the mechanisms of the model’s partial success in simulating diurnal rainfall remain ambiguous.

Diurnal Rainfall On Tropical Cyclone Cempaka And Dahlia As Observed By TRMM

Dua siklon tropis teramati di perairan bagian selatan Indonesia pada akhir 2017, menjadi siklon tropis pertama dan kedua yang terjadi di wilayah tanggung jawab Indonesia setelah siklon tropis Bakung pada 2010. Siklon tropis Cempaka terbentuk di perairan sebelah selatan Provinsi Jawa Tengah dan menyebabkan curah hujan tinggi di wilayah selatan pulau Jawa. Siklon tropis Dahlia terbentuk di sebelah selatan Provinsi Banten dengan pengaruh yang lebih kecil terhadap curah hujan di daratan disebabkan jarak yang lebih jauh. Tujuan dari penelitian ini adalah untuk mengetahui siklus harian curah hujan yang terjadi pada kedua siklon tropis tersebut, serta siklus harian yang terjadi pada wilayah terdampak saat terjadi siklon tropis. Data yang digunakan pada penelitian ini adalah curah hujan rata-rata per tiga jam dari Tropical Rainfall Measurement Mission (TRMM), khususnya data 3B42RT. Metode yang digunakan pada penelitian ini adalah analisis time series. Hasil dari penelitian ini menunjukkan bahwa ketika terjadi siklon tropis, curah hujan mencapai puncak pada malam sampai dini hari, kemudian melemah pada pagi sampai sore hari. Pada daerah terdampak di daratan, puncak hujan terjadi pada siang dan malam hari, dan melemah pada sore dan dini hari.