Pedro Ortiz

and 4 more

Collection of increasingly voluminous multi-spectral data from multiple instruments with high spatial resolution has posed both an opportunity and a challenge for maximizing their utilization, analysis, and impact. Obtaining accurate estimates of precipitation globally with high temporal resolution is crucial for assessing multi-scale hydrologic impacts and providing a constraint for development of numerical models of the atmosphere that provide weather and climate predictions. Precipitation type classification plays an important role in constraining both the inverse problem in satellite precipitation retrievals and latent heat transfer within weather prediction simulations. Precipitation type, however, is often reported deterministically, without uncertainty attached to an estimate. Machine learning techniques are capable of extracting content of interest from large datasets and accurately retrieving discrete and continuous properties of physical systems, but with limited insights to the retrieval components–such as errors and the physical relationship between the observed and retrieved properties. To address this shortcoming, we perform precipitation type classification to introduce a novel tool for decomposing errors of satellite-retrieved products. We use Bayesian neural networks to map Global Precipitation Measurement mission Microwave Imager observations to Dual-frequency Precipitation Radar-derived precipitation type, which perform comparably to deterministic models, but with the added benefit of providing well calibrated uncertainties. Through uncertainty decomposition, we demonstrate well calibrated uncertainties as useful for making decisions concerning high uncertainty predictions, model selection, targeted data analysis, and data collection and processing. Additionally, our Bayesian models enable mathematical confirmation of a data distribution change as the cause for an unacceptable decline in model accuracy.

Lisa Milani

and 3 more

Quantitative Precipitation Estimates from space-based observations represent an important dataset for understanding the Earth’s atmospheric, hydrological and energy cycles. Precipitation retrieval algorithms have been developed and refined over the last few decades and their accuracy and reliability are becoming increasingly more important for Earth’s energy budget and human activities. In particular, snowfall represents a key component of water cycle and contributes significantly to the Earth’s radiative balance. Accurately quantifying global surface snowfall is especially important since snow comprises a large percentage of the annual surface precipitation in many regions. The complexity of snowflakes particles and the nonlinear relationships between observations and retrieved variables have moved scientists to continually develop and enhance retrieval techniques. The present work aims to improve snowfall retrievals from Passive Microwave (PMW) sensors. Within the Global Precipitation Measurement (GPM) mission, the Goddard PROFiling (GPROF) algorithm snowfall retrieval has been chosen as an example of PMW precipitation product. Since previous works have demonstrated that GPROF performance strongly depends on the snowfall type, we developed a Machine Learning technique to classify snowing regime. A combined CloudSat-GPM dataset has been used to build the training dataset in which the GPM Microwave Imager (GMI) brightness temperatures (TB) are associated with a snowfall type, classifying the snowfall into three classes (‘shallow convective’, ‘deep stratiform’, ‘other’). The snowfall classification was adopted from a CloudSat classifying technique, based on snowing profiles and cloud classification. The problem is posed as a supervised learning problem, using a fully connected deep learning architecture with TB textures serving as input features. After building, optimizing and applying the classification method to existing GMI data, an evaluation exercise was undertaken to assess the classification performance. Results show that using only 20,000 GMI-CloudSat collocated snowing scenes the accuracy in retrieving the three classes has exceeded 80%. Being able to classify snowfall mode will help develop a specific setup for GPROF to improve detection and retrieval performance.