Author Topic: What is the Definition of a Rain Day or a Wet Day? (Read 24441 times)

JennyLeez · « **on:** July 16, 2012, 07:32:30 PM »

I know this has been covered in other forums but having asked a few members of late I have been given varied answers.
So here we go.

What do you class as a Rain day?
What do you class as a Wet day?
and What do you class as a Precipitation Day.

Mark · « **Reply #1 on:** July 16, 2012, 08:06:42 PM »

A day that had some rain[/color]
What do you class as a Wet day? A day when its rained most of the day
and What do you class as a Precipitation Day.A day (24hours)When you have recorded rain

David · « **Reply #2 on:** July 16, 2012, 08:08:14 PM »

Rain day = any rainfall that is enough to record in a rain gauge
Wet day = any day with rainfall >= 1.0mm

JennyLeez · « **Reply #3 on:** July 16, 2012, 08:42:31 PM »

Ok I was given this.
Precip day or rain day = 0.2mm or more.
Wet Day = 1.0mm or more

Food for thought.
Now Cumulus users dont show any rain until 1 tip and that 1 tip would = 0.3mm.
Therefore Cumulus users would never have a reading of 0.2mm where as WD users would.
So do WD users have more of a chance of a rain day over Cumulus users

There is also a 50% chance if that is the total for the day that it in fact be dew and not rain....yes?

David · « **Reply #4 on:** July 16, 2012, 08:55:50 PM »

The tip amount depends on the rain gauge, not the weather software. After one tip Cumulus shows 0.2mm for me

RobertHH · « **Reply #5 on:** July 16, 2012, 09:27:43 PM »

Fortunately, or unfortunately, how you define the various descriptions of rainfall is vague. It is a good thing in some respects, as the ability of some equipment to measure rainfall is suspect, because the mechanics, electronics and software employed do not provide a consistent result. It is also quite good to keep the definitions vague because rain gauge catchment areas are generally too small to provide accurate measurement of small amounts of rainfall. Rainfall expressed in mm per square meter or Litres per square meter is a simple and recognised standard and your ability to measure low levels of rainfall depends on the size of the catchment and its placement relative to any other objects. This is nicely vague, it depends what you have and where it is, relative to your own definition of rainfall, relative to your ability to measure it. My own personal view is that if it is raining or has been raining, it is a wet day, but to quantify it, I use anything above 0.04 mm as the definition of a wet day but in my system that represents a collected rainfall in excess of 2 Litres. I don't actually think that there is significant benefit from splitting the definitions beyond wet or dry unless it is coupled to other factors which can give an indication of its effect or relationship to a particular area.

deepsouthweather · « **Reply #6 on:** July 16, 2012, 10:39:48 PM »

Just to throw in my thoughts. NIWA considers a rain day is 1.0mm or more (according to thier historical averages for rain days) . I see alot of wx stations on this forum regularly record 0.2/0.3mm daily & from my own experience especially in winter this is caused more often than not by dew which from my research does not constitute percipitation unless it was fog! I edit out these 0.2's as I catch them to keep my percipitation stats correct, Some later version Cumulus have since last dry/wet day which restarts the count as soon as the bucket has tipped.

TokWW · « **Reply #7 on:** July 16, 2012, 11:12:01 PM »

The Bureau of Metrology in AU:

Rain day
A rain day occurs when a daily rainfall of at least 0.2 mm is recorded.

In the States, NOAA defines a rain day as greater or equal to .01" = 1/100" = 0.25mm

RobertHH · « **Reply #8 on:** July 17, 2012, 10:49:56 AM »

Perhaps the Australian definitions are appropriate for most purposes :

Extreme Temperature Indices    Definition
Very hot days    Annual count of days with maximum temperature > 40°C
Hot days    Annual count of days with maximum temperature > 35°C
Very hot nights    Annual count of nights with minimum temperature > 25°C
Hot nights    Annual count of nights with minimum temperature > 20°C
Cold days    Annual count of days with maximum temperature < 15°C
Very cold days    Annual count of days with maximum temperature < 10°C
Cold nights    Annual count of nights with minimum temperature < 5°C
Frost nights    Annual count of nights with minimum temperature < 0°C
Warm days    Percentage of days with maximum temperature > 90th percentile
Warm nights    Percentage of nights with minimum temperature > 90th percentile
Cool days    Percentage of days with maximum T < 10th percentile
Cool nights    Percentage of nights with minimum T < 10th percentile
Highest maximum temperature    Annual maximum value of daily maximum temperature
Highest minimum temperature    Annual maximum value of daily minimum temperature
Lowest maximum temperature    Annual minimum value of daily maximum temperature
Lowest minimum temperature    Annual minimum value of daily minimum temperature
Warm spell duration    Annual count of days with at least 4 consecutive days when daily maximum temperature > 90th percentile
Cold spell duration    Annual count of nights with at least 4 consecutive nights when daily minimum temperature < 10th percentile
Growing season length    Annual (1st July to 30th June) count between first span of 6 or more days with daily mean temperature > 15°C and first span of 6 or more days with daily mean temperature < 15°C
Extreme Precipitation Indices    Definition
Wet days    Annual count of days with daily precipitation ≥ 1 mm
Heavy precipitation days    Annual count of days with daily precipitation ≥ 10 mm
Very heavy precipitation days    Annual count of days with daily precipitation ≥ 30 mm
Maximum 1-day precipitation    Annual maximum 1-day precipitation total
Maximum 5-day precipitation    Annual maximum consecutive 5-day precipitation total
Very wet day precipitation    Annual total precipitation when daily precipitation > 95th percentile
Extremely wet day precipitation    Annual total precipitation when daily precipitation > 99th percentile
Annual total wet day precipitation    Annual total precipitation on wet days (daily precipitation ≥ 1 mm)
Simple daily intensity    Annual total precipitation divided by the number of wet days (daily precipitation ≥ 1 mm)
Consecutive dry days    Maximum number of consecutive days with daily precipitation < 1 mm
Consecutive wet days    Maximum number of consecutive days with daily precipitation ≥ 1 mm

Weather Display · « **Reply #9 on:** July 17, 2012, 06:54:14 PM »

WD can be set to ignore a tip that is dew

JennyLeez · « **Reply #10 on:** July 17, 2012, 07:59:16 PM »

Cumulus Users have to manually remove.
Thats easy enough but unfortunately it does not correct the last 24 hour value or last hour. If you wish to correct those it means mucking around with day files.
Definitely not ideal.

deepsouthweather · « **Reply #11 on:** July 17, 2012, 09:38:34 PM »

Cumulus could have been setup better in that respect. But the day files are where I do it from. Just have to remember cumulus cant be running when you edit them.

JennyLeez · « **Reply #12 on:** July 17, 2012, 10:08:47 PM »

Yep same here.
Steve fixed this a week ago. So thats a help

Quote

Fix for high hourly rain timestamp being set when no rain

Babs · « **Reply #13 on:** July 18, 2012, 05:23:46 PM »

A rain day is when I think about staying in bed all day and a wet day is when I do just that. A good book, a hot drink to sip and a snuggly bed, a day dreams are made of is a wet day on the hill top!

hotcop65 · « **Reply #14 on:** July 23, 2012, 08:23:20 AM »

My thoughts exactly Babs. Well put

Babs · « **Reply #15 on:** July 25, 2012, 10:59:37 AM »

Its a wet day I should be in bed!

TokWW · « **Reply #16 on:** July 25, 2012, 03:11:17 PM »

But going to restaurants and eating chocolate cake is ok...

Babs · « **Reply #17 on:** July 25, 2012, 07:57:09 PM »

thats what you do on a rain day haha

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Author Topic: What is the Definition of a Rain Day or a Wet Day? (Read 24441 times)