The Chalmers Cloud Ice Climatology: A novel, robust climate record of
frozen cloud hydrometeor concentrations
Abstract
Frozen cloud particles are an important link in the hydrological cycle
and significantly influence the Earth’s energy budget. Despite their
important role, observational records constraining concentrations of
atmospheric ice remain severely limited. While combined radar and lidar
estimates from the CloudSat and CALIPSO missions offer over a decade of
high-quality data on ice hydrometeor concentrations, these estimates
remain sparse. In contrast, products derived from passive satellite
sensors typically provide better spatiotemporal coverage but disagree
with CloudSat-baed measurements.
To address these limitations, we present a novel climate data record of
total ice water path (TIWP), the Chalmers Cloud Ice Climatology (CCIC).
It spans 40 years, from 1983 to the present, covering latitudes from 70
degree South to 70 degree North. CCIC offers TIWP estimates at
three-hourly resolution from 1983 and half-hourly resolution from 2000
onwards. We demonstrate the long-term stability of CCIC by directly
comparing it with CloudSat/CALIPSO-based estimates over the entire
mission lifetime. Additionally, we assess CCIC against other long-term
TIWP records, revealing that CCIC yields most accurate TIWP estimates
compared to CloudSat/CALIPSO-based reference estimates. An investigation
of the regional trends in TIWP shows good agreement between four
observational datasets and ERA5 for the most recent 20 years. However,
the consistency decreases for 40-year trends.
The CCIC climate record closes the gap between existing long-term TIWP
records and CloudSat/CALIPSO-based reference measurements. The
estimates’ continuous coverage and demonstrated accuracy make it a
valuable resource for lifecycle studies of storms and the analysis of
fine-scale cloud features in a changing climate.