User Panel
User Panel
User Panel
|
Posted: 10/23/2013 5:40:32 PM EDT
[#1]
Is this a serious question?
|
|
|
|
Posted: 10/23/2013 5:41:16 PM EDT
[#2]
My answer depends on how you voted in the intelligence thread.
|
|
|
|
Posted: 10/23/2013 5:41:23 PM EDT
[#3]
Yes.
|
|
|
|
Posted: 10/23/2013 5:41:27 PM EDT
[#4]
yes its possible.
You trying to protect plants? |
|
|
|
Posted: 10/23/2013 5:43:37 PM EDT
[#5]
Is frost possible at a temperature below that which water freezes at? Yes, in fact it is.
|
|
|
|
Posted: 10/23/2013 5:46:08 PM EDT
[#6]
I would assume that yes it can occur at those temps at or near ground level. Typically if its going to be 28 and breezy it wont get that cold however if there is no inversion or you are in a cold air mass then it will just be 28 and breezy. I grow fruit trees and in the spring predominantly (sometimes in the winter) we run what we call wind machines. They are basically big fans on like a 30' tower that suck warm air down from higher up and push the cold air out from ground level bring temps up and keeping them above critical for killing our flower buds. Most times this works but sometimes it just gets too cold, or there is no warm air up high (no inversion layer), and things freeze. Hope this helps.
|
|
|
|
Posted: 10/23/2013 6:01:27 PM EDT
[#7]
Hell, I live in La, where frost appears once every 20,000 years and I know the answer to that question.
 
|
|
|
|
Posted: 10/23/2013 6:02:05 PM EDT
[#8]
Quote HistoryQuoted:
Is this a serious question? Yes. |
|
|
|
Posted: 10/23/2013 6:03:09 PM EDT
[#9]
Quote HistoryQuoted:
My answer depends on how you voted in the intelligence thread. Now that was just mean spirited. Bless your heart. 
|
|
|
|
Posted: 10/23/2013 6:03:41 PM EDT
[#10]
Quote HistoryQuoted:
Yes. Quote HistoryQuoted:
Quoted:
Is this a serious question? Yes. Yes,it is possible. |
|
|
|
Posted: 10/23/2013 6:04:09 PM EDT
[#11]
Quote HistoryQuoted:
yes its possible. You trying to protect plants? Yes. Trying to keep some garden plants alive over the next few days until they can "weather the storm". |
|
|
|
Posted: 10/23/2013 6:04:56 PM EDT
[#12]
Quote HistoryQuoted:
Yes. Trying to keep some garden plants alive over the next few days until they can "weather the storm". Quote HistoryQuoted:
Quoted:
yes its possible. You trying to protect plants? Yes. Trying to keep some garden plants alive over the next few days until they can "weather the storm". If you run a sprinkler they won't freeze. |
|
|
|
Posted: 10/23/2013 6:05:15 PM EDT
[#13]
Quote HistoryQuoted:
Is frost possible at a temperature below that which water freezes at? Yes, in fact it is. Need some details. That was why I was asking! 
|
|
|
|
Posted: 10/23/2013 6:05:38 PM EDT
[#14]
Sprinkler is your friend here..
|
|
|
|
Posted: 10/23/2013 6:05:53 PM EDT
[#15]
Wind doesn't effect the temperature of water freezing, either.
|
|
|
|
Posted: 10/23/2013 6:06:18 PM EDT
[#16]
frost possible at 32 or below, it has nothing to do with wind.
|
|
|
|
Posted: 10/23/2013 6:06:56 PM EDT
[#17]
Quote HistoryQuoted:
Yes. Trying to keep some garden plants alive over the next few days until they can "weather the storm". Quote HistoryQuoted:
Quoted:
yes its possible. You trying to protect plants? Yes. Trying to keep some garden plants alive over the next few days until they can "weather the storm". Cover them or if potted bring them in |
|
|
|
Posted: 10/23/2013 6:08:42 PM EDT
[#18]
Quote HistoryQuoted:
My answer depends on how you voted in the intelligence thread. 
|
|
|
|
Posted: 10/23/2013 6:10:11 PM EDT
[#19]
It can actually frost with the air temp above freezing.
|
|
|
|
Posted: 10/23/2013 6:10:22 PM EDT
[#20]
Down here further south (Think Houston but 45 miles north) have seen it many a times.
Maybe high 30's very low 40's and have frost on the windshield in the morning. OP, have you never seen this? Really? How old are you OP? 10? 12?
|
|
|
|
Posted: 10/23/2013 6:11:34 PM EDT
[#21]
Yes. 25 degrees this morning, all cars with a thick layer of frost.
|
|
|
|
Posted: 10/23/2013 6:12:58 PM EDT
[#22]
If you have a clear night with no wind, that is no clouds AND the dew point gets under 32 F, you can have frost even if the air temperature is above freezing. This is radiational cooling. Deep space is at 4 Kelvin, the plants are at around 290 Kelvin. Heat transfers via black body radiation at the power of 5.67 x 10-8 Watts/meter2 K4where K is the difference between the hot item and cold sink raised to the 4th. So a 1 square meter black surface at 290 K would radiate over 350 watts of heat on a clear night.
Now plants are not perfect black body radiators, give them an emittance of 0.35 or so...depends on species etc. |
|
|
|
Posted: 10/23/2013 6:14:02 PM EDT
[#23]
Normally,the 1st frost can occur if the sky is clear,and the air is still. I have seen frost when it the thermometer showed 35F,but certain areas of yard were colder. I have had success with washing plants the night before with hose,then washing them again BEFORE the sun comes up. I have a greenhouse,and If I miss judge a frost,and don't get cuttings in in time can lose a whole years crop.
|
|
|
|
Posted: 10/23/2013 6:15:01 PM EDT
[#24]
Frost can less likely at 33ºF and a little bit of wind than at 35ºF and no wind.
Thermal radiation. ETA: Keith_J, sometimes I hate you. But, I mean that in the nicest possible way. The atmosphere is a participating medium with respect to thermal radiation, especially at longer, emissive wavelengths. But, Keith's example is a good first-order approximation. 350+ W/m^2 lost to the blackness of space, compared to roughly1360 W/m^2 of incident (normal) solar radiation from the sun. But, integrate over time, and you have a rather curious balance. |
|
|
|
Posted: 10/23/2013 6:20:37 PM EDT
[#25]
Quote HistoryQuoted:
I would assume that yes it can occur at those temps at or near ground level. Typically if its going to be 28 and breezy it wont get that cold however if there is no inversion or you are in a cold air mass then it will just be 28 and breezy. I grow fruit trees and in the spring predominantly (sometimes in the winter) we run what we call wind machines. They are basically big fans on like a 30' tower that suck warm air down from higher up and push the cold air out from ground level bring temps up and keeping them above critical for killing our flower buds. Most times this works but sometimes it just gets too cold, or there is no warm air up high (no inversion layer), and things freeze. Hope this helps. Thank you! It does! :) |
|
|
|
Posted: 10/23/2013 6:24:06 PM EDT
[#26]
Quote HistoryQuoted:
Cover them or if potted bring them in Quote HistoryQuoted:
Quoted:
Quoted:
yes its possible. You trying to protect plants? Yes. Trying to keep some garden plants alive over the next few days until they can "weather the storm". Cover them or if potted bring them in Will be doing that over the next few days. Seems like at the years end, it is always a struggle to keep plants alive until they finish producing. Good advice Matt! :) |
|
|
|
Posted: 10/23/2013 6:27:52 PM EDT
[#27]
Quote HistoryQuoted:
It can actually frost with the air temp above freezing. With no wind, I have seen it happen. Seems like when a little wind is present, it doesn`t happen....for the MOST part. Can`t tell you with any certainty, what the specific temp. was at the time. Just remembered it was near freezing. Sometimes frost, other times none. |
|
|
|
Posted: 10/23/2013 6:29:49 PM EDT
[#28]
Quote HistoryQuoted:
Wind doesn't effect the temperature of water freezing, either. Sure it does. But by evaporation, not windchill. |
|
|
|
Posted: 10/23/2013 6:30:17 PM EDT
[#29]
Quote HistoryQuoted:
Down here further south (Think Houston but 45 miles north) have seen it many a times. Maybe high 30's very low 40's and have frost on the windshield in the morning. OP, have you never seen this? Really? How old are you OP? 10? 12? Late 40`s. Temps like what you just described, no frost ever. At least not here anyway.
|
|
|
|
Posted: 10/23/2013 6:32:11 PM EDT
[#30]
Quote HistoryQuoted:
Yes. 25 degrees this morning, all cars with a thick layer of frost. If it hits that here, I am sure it won`t matter. Everything would be toast at that point. |
|
|
|
Posted: 10/23/2013 6:32:35 PM EDT
[#31]
Quote HistoryQuoted:
If it hits that here, I am sure it won`t matter. Everything would be toast at that point. Quote HistoryQuoted:
Quoted:
Yes. 25 degrees this morning, all cars with a thick layer of frost. If it hits that here, I am sure it won`t matter. Everything would be toast at that point. Not if you run a sprinkler. |
|
|
|
Posted: 10/23/2013 6:34:57 PM EDT
[#32]
Quote HistoryQuoted:
If you have a clear night with no wind, that is no clouds AND the dew point gets under 32 F, you can have frost even if the air temperature is above freezing. This is radiational cooling. Deep space is at 4 Kelvin, the plants are at around 290 Kelvin. Heat transfers via black body radiation at the power of 5.67 x 10-8 Watts/meter2 K4where K is the difference between the hot item and cold sink raised to the 4th. So a 1 square meter black surface at 290 K would radiate over 350 watts of heat on a clear night. Now plants are not perfect black body radiators, give them an emittance of 0.35 or so...depends on species etc. Keith, A clear night and no wind near freezing, frost. It stinks to see those poor little plants with shriveled up leaves in the afternoon after a night of those conditions. 
|
|
|
|
Posted: 10/23/2013 6:38:48 PM EDT
[#33]
Quote HistoryQuoted:
Normally,the 1st frost can occur if the sky is clear,and the air is still. I have seen frost when it the thermometer showed 35F,but certain areas of yard were colder. I have had success with washing plants the night before with hose,then washing them again BEFORE the sun comes up. I have a greenhouse,and If I miss judge a frost,and don't get cuttings in in time can lose a whole years crop. My problem is I depend on a weatherman to let me know when it may be time to cover the plants to protect against frost. They miss the mark sometimes. At that point......................maybe next year. |
|
|
|
Posted: 10/23/2013 6:43:28 PM EDT
[#34]
That whole FPNI phenomenon is just un-fucking-canny.
|
|
|
|
Posted: 10/23/2013 6:43:34 PM EDT
[#35]
Quote HistoryQuoted:
Not if you run a sprinkler. Quote HistoryQuoted:
Quoted:
Quoted:
Yes. 25 degrees this morning, all cars with a thick layer of frost. If it hits that here, I am sure it won`t matter. Everything would be toast at that point. Not if you run a sprinkler. Never have tried that BC. I have seen that done in some movies on TV but always thought it was Hollywood. Never really gave it any thought. |
|
|
|
Posted: 10/23/2013 6:47:36 PM EDT
[#36]
Quote HistoryQuoted:
Yes. Quote HistoryQuoted:
Quoted:
Is this a serious question? Yes. I am really at a loss for words then. |
|
|
|
Posted: 10/24/2013 2:54:21 AM EDT
[#37]
Quote HistoryQuoted: I am really at a loss for words then. Quote HistoryQuoted: Quoted: Quoted: Is this a serious question? Yes. I am really at a loss for words then. |
|
|
|
Posted: 10/25/2013 8:59:42 PM EDT
[#38]
It`s 31 here tonight. Predicted temps. are 28. The previous lowest in 2 nights of frost predictions where the weatherman said it would get to 33 one night and 32 the next were the first night, 37 and low frost. The second night, 37 and more frost. Both nights were cloudy and a little wind blowing.
Clear skies and no wind tonight. Plants are covered in plastic. Here comes the litmus test. |
|
|
|
Posted: 10/25/2013 11:24:56 PM EDT
[#39]
Quote HistoryQuoted:
It`s 31 here tonight. Predicted temps. are 28. The previous lowest in 2 nights of frost predictions where the weatherman said it would get to 33 one night and 32 the next were the first night, 37 and low frost. The second night, 37 and more frost. Both nights were cloudy and a little wind blowing. Clear skies and no wind tonight. Plants are covered in plastic. Here comes the litmus test. The atmosphere can be above freezing and frost can form. It has to do with the air pressure, humidity, and the difference in temperature between the air and the objects on the ground. Complex stuff, as KeithJ pointed out. I think the warmest I can recall frost damage to crops was 38 degrees in northern Florida and southern Georgia. It was an odd event, but it happens. The term is hoar frost. |
|
|
|
Posted: 10/26/2013 2:26:46 AM EDT
[#40]
Th same thing causes dew to form even when there is no fog. Plants, roofs and anything with a high emissivity cools down to the dew point of the air. Bam.
Now, if the air's dew point is below freezing, the humidity forms frost instead of dew drops. This is deposition which forms highly reflective crystals of water, making the frost very white instead of glare ice. Emissivity is the characteristic of releasing radiant energy. It is analogous to "blackness" or the ability of an object to get warm from radiant energy. It is the opposite of reflectivity. |
|
|
|
Posted: 10/26/2013 2:53:26 AM EDT
[#41]
Quote HistoryQuoted:
If you have a clear night with no wind, that is no clouds AND the dew point gets under 32 F, you can have frost even if the air temperature is above freezing. This is radiational cooling. Deep space is at 4 Kelvin, the plants are at around 290 Kelvin. Heat transfers via black body radiation at the power of 5.67 x 10-8 Watts/meter2 K4where K is the difference between the hot item and cold sink raised to the 4th. So a 1 square meter black surface at 290 K would radiate over 350 watts of heat on a clear night. Now plants are not perfect black body radiators, give them an emittance of 0.35 or so...depends on species etc. Bill nye? 
|
|
|
|
Posted: 10/26/2013 3:15:23 AM EDT
[#42]
Quote HistoryQuoted:
Is frost possible at a temperature below that which water freezes at? Yes, in fact it is. Yup |
|
|
|
Posted: 10/26/2013 8:04:25 AM EDT
[#43]
Looking up some thermal emissivity values for various leaves, I was surprised to see they are all pretty consistent around 0.96.
http://www.icess.ucsb.edu/modis/EMIS/html/leaf.html For thermal radiation losses as a function of sky conditions: 75 W/m^2 for a clear desert night, for a typical sky-facing surface at 80ºF 60 W/m^2 with atmospheric humidity 40 W/m^2 with 50% cloud cover 7 W/m^2 with completely overcast skies http://www.fsec.ucf.edu/en/publications/pdf/FSEC-CR-1502-05.pdf |
|
|
Win a FREE Membership!
Sign up for the ARFCOM weekly newsletter and be entered to win a free ARFCOM membership. One new winner* is announced every week!
You will receive an email every Friday morning featuring the latest chatter from the hottest topics, breaking news surrounding legislation, as well as exclusive deals only available to ARFCOM email subscribers.
AR15.COM is the world's largest firearm community and is a gathering place for firearm enthusiasts of all types.
From hunters and military members, to competition shooters and general firearm enthusiasts, we welcome anyone who values and respects the way of the firearm.
Subscribe to our monthly Newsletter to receive firearm news, product discounts from your favorite Industry Partners, and more.
Copyright © 1996-2024 AR15.COM LLC. All Rights Reserved.
Any use of this content without express written consent is prohibited.
AR15.Com reserves the right to overwrite or replace any affiliate, commercial, or monetizable links, posted by users, with our own.
