The Diurnal Cycle of Precipitation: A Comparison of State-of-the-Art Observations and Models

2020 ◽  
Author(s):  
Daniel Watters ◽  
Alessandro Battaglia ◽  
Richard Allan
Keyword(s):  
Diurnal Cycle ◽  
State Of The Art ◽  
Central Africa ◽  
Coupled Model ◽  
Dual Frequency ◽  
Infrared Sensors ◽  
Precipitation Timing ◽  
Early Afternoon ◽  
Diurnal Cycle Of Precipitation ◽  
Global Precipitation

<p>Representation of the diurnal cycle is a key trial of the ability of models to capture precipitation timing, duration, and intra-daily variations.  The state-of-the-art model simulations from the Coupled Model Intercomparison Project (CMIP6), which are set to inform the upcoming IPCC sixth assessment report, are yet to be compared to the diurnal cycle of precipitation according to observations.  The recently released version 6 of the Integrated Multi-Satellite Retrievals for Global Precipitation Measurement (IMERG) product provides over 19 years of global-gridded observations (June 2000 - Present).  Such state-of-the-art observations, with inputs from space-borne dual-frequency radar, microwave radiometers, infrared sensors and ground-based gauges, have never been available at 0.1˚ gridding every half hour over such a long period.  This study aims to compare the amplitude and time of maximum precipitation accumulation between IMERG observations and CMIP6 models over an 8-year period (June 2000 – May 2008).  Preliminary results suggest that the CMIP6 models typically underestimate the amplitude of precipitation accumulation over land compared to observations, though there are overestimates in the Amazon and across central Africa.  Furthermore, the CMIP6 models typically lag behind observations in their time of maximum accumulation over land; observations suggest a late evening to night maximum whilst CMIP6 models show a late morning to early afternoon maximum.  The results will be beneficial to improving modelling of precipitation across the globe.</p>

scholarly journals The Summertime Diurnal Cycle of Precipitation Derived from IMERG

2019 ◽  
Vol 11 (15) ◽  
pp. 1781 ◽  
Author(s):  
Daniel Watters ◽  
Alessandro Battaglia
Keyword(s):  
Diurnal Cycle ◽  
Coastal Waters ◽  
Least Squares Method ◽  
Random Errors ◽  
Diurnal Cycles ◽  
Precipitation Measurement ◽  
Diurnal Cycle Of Precipitation ◽  
Global Precipitation Measurement ◽  
Global Precipitation ◽  
Latitudinal Band

The Integrated Multi-satellitE Retrievals for GPM (IMERG) precipitation product derived from the Global Precipitation Measurement (GPM) constellation offers a unique opportunity of observing the diurnal cycle of precipitation in the latitudinal band 60 ° N–S at unprecedented 0.1 ° × 0.1 ° and half-hour resolution. The diurnal cycles of occurrence, intensity and accumulation are determined using four years of data at 2 ° × 2 ° resolution; this study focusses on summertime months when the diurnal cycle shows stronger features. Harmonics are fitted to the diurnal cycle using a non-linear least squares method weighted by random errors. Results suggest that mean-to-peak amplitudes for the diurnal cycles of occurrence and accumulation are greater over land (generally larger than 25% of the diurnal mean), where the diurnal harmonic dominates and peaks at ~16–24 LST, than over ocean (generally smaller than 25%), where the diurnal and semi-diurnal harmonics contribute comparably. Over ocean, the diurnal harmonic peaks at ~0–10 LST (~8–15 LST) over open waters (coastal waters). For intensity, amplitudes of the diurnal and semi-diurnal harmonics are generally comparable everywhere (~15–35%) with the diurnal harmonic peaking at ~20–4 LST (~3–12 LST) over land (ocean), and the semi-diurnal harmonic maximises at ~5–8 LST and 17–20 LST. The diurnal cycle of accumulation is dictated by occurrence as opposed to intensity.

scholarly journals Investigating the diurnal cycle of precipitation over Central Africa

2021 ◽  
Vol 28 (4) ◽  
Author(s):  
P. C. Choumbou ◽  
A. J. Komkoua Mbienda ◽  
G. M. Guenang ◽  
D. Monkam ◽  
F. Mkankam Kamga
Keyword(s):  
Diurnal Cycle ◽  
Central Africa ◽  
Diurnal Cycle Of Precipitation

scholarly journals The Diurnal Cycle of Precipitation According to Multiple Decades of Global Satellite Observations, Three CMIP6 Models, and the ECMWF Reanalysis

2021 ◽  
pp. 1-58
Author(s):  
Daniel Watters ◽  
Alessandro Battaglia ◽  
Richard P. Allan
Keyword(s):  
Diurnal Cycle ◽  
State Of The Art ◽  
Microwave Radiometer ◽  
Mountainous Regions ◽  
Diurnal Cycles ◽  
Radar Network ◽  
Precipitation Measurement ◽  
Diurnal Cycle Of Precipitation ◽  
Spatio Temporal ◽  
June July

AbstractNASA Precipitation Measurement Mission observations are used to evaluate the diurnal cycle of precipitation from three CMIP6 models (NCAR-CESM2, CNRM-CM6-1, CNRM-ESM2-1) and the ERA5 reanalysis. NASA’s global-gridded IMERG product, which combines spaceborne microwave radiometer, infrared sensor and ground-based gauge measurements, provides high spatio-temporal resolution (0.1°, half-hourly) estimates that are suitable for evaluating the diurnal cycle in models, as determined against the CONUS ground-based radar network. IMERG estimates are coarsened to the spatial and hourly resolution of the state-of-the-art CMIP6 and ERA5 products, and their diurnal cycles are compared across multiple decades of June-July-August in the 60°N–S domain (IMERG and ERA5: 2000–2019; NCAR and CNRM: 1979–2008). Low precipitation regions (and weak amplitude regions when analyzing the diurnal phase) are excluded from analyses in order to assess only robust diurnal signals. Observations identify greater diurnal amplitudes over land (26–134% of the precipitation mean; 5th–95th percentile) than over ocean (14–66%). ERA5, NCAR and CNRM underestimate amplitudes over ocean, whilst ERA5 overestimates over land. IMERG observes a distinct diurnal cycle only in certain regions, with precipitation peaking broadly between 14–21 LST over land (21–6 LST over mountainous and varying-terrain regions) and 0–12 LST over ocean. The simulated diurnal cycle is unrealistically early compared with observations, particularly over land (NCAR-CESM2-AMIP: –1 hour; ERA5: –2 hours; CNRM-CM6-1-AMIP: –4 hours on average) with nocturnal maxima not well represented over mountainous regions. Furthermore, ERA5’s representation of the diurnal cycle is too simplified, with less interannual variability in the time of maximum compared to observations over many regions.

scholarly journals Potential effects of aerosols on the diurnal cycle of precipitation over Central Africa by RegCM4.4

2019 ◽  
Vol 1 (2) ◽  
Author(s):  
A. J. Komkoua Mbienda ◽  
G. M. Guenang ◽  
R. S. Tanessong ◽  
A. Tchakoutio Sandjon
Keyword(s):  
Diurnal Cycle ◽  
Central Africa ◽  
Diurnal Cycle Of Precipitation

scholarly journals A Unified Convection Scheme (UNICON). Part II: Simulation

2014 ◽  
Vol 71 (11) ◽  
pp. 3931-3973 ◽  
Author(s):  
Sungsu Park
Keyword(s):  
Diurnal Cycle ◽  
Radiative Forcing ◽  
Deep Convection ◽  
The United States ◽  
Convection Scheme ◽  
Near Surface ◽  
Surface Precipitation ◽  
Early Afternoon ◽  
Single Column ◽  
Diurnal Cycle Of Precipitation

Abstract A unified convection scheme (UNICON) is implemented into the Community Atmosphere Model, version 5 (CAM5), and tested in single-column and global simulations forced by observed sea surface temperature. Compared to CAM5, UNICON substantially improves the single-column simulations of stratocumulus-to-cumulus transition and shallow and deep convection cases. The global performance of UNICON is similar to CAM5 with a relative spatiotemporal root-mean-square error (RMSE) of 0.777 (0.755 in CAM5) against the earlier version of the model (CCSM3.5). The notable improvements in the UNICON-simulated climatologies over CAM5 are seasonal precipitation patterns (i.e., monsoon) over the western Pacific and South Asia, reduced biases of cloud radiative forcing in the tropical deep convection regions, aerosol optical depth in the tropical and subtropical regions, and cumulus fraction and in-cumulus condensate. One notable degradation is that UNICON simulates warmer near-surface air temperature over the United States during summer. In addition to the climatology, UNICON significantly improves the simulation of the diurnal cycle of precipitation and the Madden–Julian oscillation (MJO). The surface precipitation simulated by UNICON is a maximum in the late afternoon (early afternoon in CAM5) over the summer continents and in the early morning (predawn in CAM5) over the ocean with a fairly realistic amplitude of the diurnal cycle. Sensitivity simulations indicate that the key for successful MJO simulation in UNICON is a seamless parameterization of the updraft plume dilution rate as convection evolves from shallow to deep convection. The mesoscale perturbation of the vertical velocity and the thermodynamic scalars of convective updrafts is an additional requirement for simulating the observed diurnal cycle of precipitation.

scholarly journals Metrics for the Diurnal Cycle of Precipitation: Toward Routine Benchmarks for Climate Models

2016 ◽  
Vol 29 (12) ◽  
pp. 4461-4471 ◽  
Author(s):  
Curt Covey ◽  
Peter J. Gleckler ◽  
Charles Doutriaux ◽  
Dean N. Williams ◽  
Aiguo Dai ◽  
...  
Keyword(s):  
Diurnal Cycle ◽  
Climate Models ◽  
Climate Model ◽  
Coupled Model ◽  
Fourier Amplitude ◽  
Multimodel Ensemble ◽  
Intercomparison Project ◽  
Diurnal Cycle Of Precipitation ◽  
First Time ◽  
Recent Version

Abstract Metrics are proposed—that is, a few summary statistics that condense large amounts of data from observations or model simulations—encapsulating the diurnal cycle of precipitation. Vector area averaging of Fourier amplitude and phase produces useful information in a reasonably small number of harmonic dial plots, a procedure familiar from atmospheric tide research. The metrics cover most of the globe but down-weight high-latitude wintertime ocean areas where baroclinic waves are most prominent. This enables intercomparison of a large number of climate models with observations and with each other. The diurnal cycle of precipitation has features not encountered in typical climate model intercomparisons, notably the absence of meaningful “average model” results that can be displayed in a single two-dimensional map. Displaying one map per model guides development of the metrics proposed here by making it clear that land and ocean areas must be averaged separately, but interpreting maps from all models becomes problematic as the size of a multimodel ensemble increases. Global diurnal metrics provide quick comparisons with observations and among models, using the most recent version of the Coupled Model Intercomparison Project (CMIP). This includes, for the first time in CMIP, spatial resolutions comparable to global satellite observations. Consistent with earlier studies of resolution versus parameterization of the diurnal cycle, the longstanding tendency of models to produce rainfall too early in the day persists in the high-resolution simulations, as expected if the error is due to subgrid-scale physics.

The Diurnal Cycle of Precipitation: A Comparison of State-of-the-Art IMERG Observations, CMIP6 Models and ERA5 Reanalysis

2021 ◽  
Author(s):  
Daniel Watters ◽  
Alessandro Battaglia ◽  
Richard Allan
Keyword(s):  
Diurnal Cycle ◽  
Boreal Summer ◽  
Dual Frequency ◽  
Night Time ◽  
Maximum Precipitation ◽  
Mountainous Regions ◽  
Precipitation Record ◽  
Precipitation Estimates ◽  
Diurnal Cycle Of Precipitation ◽  
Improved Performance

<p>Simulations of the diurnal cycle of precipitation from CMIP6 models and the ERA5 reanalysis are evaluated against the observed diurnal cycle from NASA’s IMERG observations.  The IMERG observation product, which combines the GPM/TRMM microwave constellation, spaceborne infrared sensors and ground-based gauge measurements, provides 20+ years of gridded global precipitation estimates at 0.1˚ every half hour.  Using IMERG’s long precipitation record, the first multi-decade evaluation of the simulated diurnal cycle is conducted (IMERG and ERA5: 2000-2019; CMIP6: 1979-2008).  After spatial and temporal matching of IMERG to the hourly CMIP6 (NCAR-CESM2, CNRM-CM6-1, CNRM-ESM2-1) and ERA5 simulations, the diurnal cycle for boreal summer is compared between products across the globe (60˚N-S).  To avoid bias in the results, regions with yearly mean precipitation < 100 mm are excluded from all analyses, as well as regions with weak diurnal amplitudes when analysing the time of maximum precipitation.  CMIP6 and ERA5 simulations underestimate the observed diurnal amplitude over ocean (14-66% of the precipitation mean, for the 5<sup>th</sup>-95<sup>th</sup> percentile range), with varying performance over land (26-134%).  Maximum precipitation is observed to accumulate over land in the afternoon and at night (14-21 LST over flatter terrain, and 21-6 LST over mountainous regions), and in the morning over ocean (0-12 LST).  CMIP6 and ERA5 are identified to better simulate the time of maximum over ocean than over land, though typically earlier in the day than observed.  In particular, ERA5 and CMIP6 fail to capture the propagating night-time peaks in precipitation accumulation close to mountainous regions.  Further analyses over CONUS, which include the ground-based radar network, highlight the improved performance of models in regions susceptible to convection (e.g. the Rocky Mountains).  Furthermore, IMERG’s skill in capturing the diurnal cycle over CONUS is demonstrated, and the current capability of the GPM Core Observatory’s dual-frequency precipitation radar is assessed.</p>

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