The PMP can be used to compare observed and simulated sub-daily precipitation, including forced (the diurnal and semi-diurnal cycle) and unforced variability (often referred to as "intermittency"). Well established Fourier analysis (e.g., Dai, 2006) with well-established large scale objective performance metrics (Covey et al., 2016) to estimate the phase and amplitude of the diurnal and semi-diurnal cycle of precipitation. The unforced sub-daily variability stems from methods developed by Trenberth et al. (2017) and Covey et al. (2017). Both analysis require data at a 3hr time resolution.
Analysis of higher frequency data often includes multiple stages of processing. The flow diagram of the PMP's sub-daily precipitation shows that is the case here. Each of the steps highlighted in the flow diagram are included in the diurnal cycle and intermittency Jupyter notebook demo.
Covey, C, PJ Gleckler, C Doutriaux, DN Williams, A Dai, J Fasullo, K Trenberth, and A Berg. 2016. ”Metrics for the diurnal cycle of precipitation: Toward routine benchmarks for climate models.” Journal of Climate 29(12): 4461–4471, https://doi.org/10.1175/JCLI-D-15-0664.1
Covey, C, C Doutriaux, PJ Gleckler, KE Taylor, KE Trenberth, and Y Zhang. 2018. “High-frequency intermittency in observed and model-simulated precipitation.” Geophysical Research Letters 45(22): 12514–12522, https://doi.org/10.1029/2018GL078926
Dai, A. 2006. “Precipitation characteristics coupled climate models.” Journal of Climate 19(18): 4605–4630, https://doi.org/10.1175/JCLI3884.1
Trenberth, KE, Y Zhang, and M Gehne. 2017. ”Intermittency in precipitation: Duration, frequency, intensity, and amounts using hourly data.” Journal of Hydrometeorology 18(5): 1393–1412, https://doi.org/10.1175/JHM-D-16-0263.1