The effect of the Novel Coronavirus epidemic on weather observations

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Please note that I wrote "weather observations", not "weather" per se :-)

I'm just finishing up processing all the 2020 weather data from NCEI's ISD (National
Center for Environmental Information Integrated Surface Database), which has become a
ritual for me every January for the past decade.? When I got to processing the data for
East Asia, I was puzzled initially to get only 64 usable weather files for China, instead
of the usual 400, and? even fewer for Japan.? When I looked in the metadata, I found? this
was due to the absence of Cloud Cover information I need to calculate the solar
radiation.? Attached is a table showing the number of cloud cover reports by month,
followed by the annual average, for all ISD stations in China and Japan for 2020.

I was startled when I first looked at this table.? In China, 80% of the weather stations
all stopped reporting cloud cover in April.? In Japan,? the dropoff was even greater,
although not as uniform as in China, with many stations not reporting Cloud Cover
throughout the year,? many others stopping in February or March, leaving only 21 stations
(8%)? that had Cloud Cover data? for the entire year.

I can't find any reasonable explanation for this change except for the lockdowns due to
the pandemic.? Although weather stations have become automated everywhere, Cloud Cover
reports are still based on human observation, excepting those ASOS (Automated Surface
Observing System) stations equipped with? upward-looking lasers and ceilometers. I've
noted two years ago that Cloud Cover data have been dropping steadily in recent years (see
attached e-mail "Decline of cloud cover report in the ISD"), but what's happened? this
time in China and Japan clearly has a very different cause.? All the more reason to move
to satellite-derived solar radiation !


Joe Huang
White Box Technologies, Inc.
346 Rheem Blvd., Suite 205A
Moraga CA 94556
yjhuang at for simulation-ready weather data
(o) (925)388-0265
(c) (510)928-2683
"building energy simulations at your fingertips"

Joe Huang's picture
Joined: 2011-09-30
Reputation: 406

Joe -

The cloud cover data is also used in the algorithms for estimating the
sky temperature. Hopefully something can be figured out to either get
the cloud cover data or determine the radiation and sky temperature
values without it.


Timothy P. McDowell
Executive Vice President
Thermal Energy System Specialists, LLC
3 N Pinckney St, Suite 202
Madison, WI 53703
office: 608-274-2577
cell: 608-225-5250

Timothy McDowell's picture
Joined: 2011-10-02
Reputation: 0

NASA POWER is now providing hourly long-wave as well as short-wave radiation downwards on a 1/2 degree grid, currently on a Beta test basis to those interested. I?ve been receiving such data on a limited basis from their staff over the past year for locations not covered currently by other sources of satellite-derived solar. I?ve promised the last TC 4.2 virtual meeting I would compare the NASA?s long-wave data I have to the Berdahl Model as soon as I can convert that data to an effective sky temperature as well as code up the Berdahl Model provided me by Chip. So far I?ve only got such NASA data for locations in Japan, China, and Myanmar, but I?m intending to get NASA POWER in bulk now that it can be downloaded directly by users. I don?t want to overpromise anything as I haven?t personally used the NASA POWER portal for their solar ?products? yet.


Sent from my iPhone
Joe Huang
White Box Technologies
346 Rheem Blvd Suite 108D
Moraga CA 94556
(o) 1(925)388-0265
(c) 1(510)928-2683
yjhuang at

Joe Huang's picture
Joined: 2011-09-30
Reputation: 406